Module 2 Cause and Effect - Inferences and Generalisations PDF

4 MODULE 2 CAUSE AND EFFECT – INFERENCES AND GENERALISATIONS A scientific inquiry is commenced when a person makes an inference about an observation that is based on their current understanding. From this point scientists create hypotheses and conduct experiments to test...

4 MODULE 2 CAUSE AND EFFECT – INFERENCES AND GENERALISATIONS A scientific inquiry is commenced when a person makes an inference about an observation that is based on their current understanding. From this point scientists create hypotheses and conduct experiments to test the accuracy of their understanding. This process has led to generalisations that can be applied to the wider world, and has driven advances in scientific understanding and the development of new technologies. Scientific inferences and generalisations do not operate in isolation. A scientist’s personal experience and that of others can influence and advance knowledge in a wide range of disciplines. INQUIRY QUESTIONS What can be inferred from observations? Can secondary sources be useful in scientific investigations? How do humans recognise patterns in data? What assumptions and generalisations can be made from data? Why should assumptions and generalisations made from data be tested? What part do peers have in a scientific investigation? CONTENT Students investigate: observations and inferences developing inquiry questions using secondary-sourced data generalisations in science observing patterns peer review OUTCOMES A student: develops and evaluates questions and hypotheses for scientific investigations INS11/12-1 designs and evaluates investigations in order to obtain primary and secondary data and information INS11/12-2 selects and processes appropriate qualitative and quantitative data and information using a range of appropriate media INS11/12-4 examines the use of inferences and generalisations in scientific investigations INS11-9 Investigating Science Stage 6 Syllabus © NSW Education Standards Authority for and on behalf of the Crown in right of the State of New South Wales, 2017 76 9780170411196 9780170411196 Shutterstock.com/ChameleonsEye 77  4.1 Observations and inferences Making inferences Getty Images/Blend Images/John Lund When people observe something happen that is novel or unique it often captures their interest; they become curious as to why it happened and begin to think about possible causes for the effect observed. For example, when an audience watches a magic show they respond to the illusions in a number of ways depending on their personal experiences. This is because each individual’s assumption past experiences leads them to make assumptions about idea in the form of an inference that was how the world works. In the magic show example, nearly established in the past everyone would assume that objects fall when they have and is used to inform another inference no support due to years of experience with objects doing FIGURE 4.1.1 Past experience with objects that inference just that, yet the magician’s illusion causes the audience fall without support would lead most people to infer that there is a hidden means of supporting conclusion that is to become amazed because objects appear to do just the the woman in this illusion. rationally and logically made based on opposite. From this apparent contradiction the audience observations and will begin to make a number of inferences about the trick available information they have observed. They can infer that there must be some kind of support or wires holding the woman scientific process systematic process up, which aligns with their past experience, or they can infer that the magician really can defy gravity. whereby questions The process of inferring possible explanations for observed phenomena is an integral part of the are answered and hypotheses tested to scientific process. Inferences are made based on past experiences, assumptions, available evidence generate empirical and collective understanding about how the world works. An inference can be tested by developing evidence hypotheses and the scientific process can be used to eliminate potential sources of error. Following these generalisation idea or conclusion that steps, a generalisation about the phenomena can be developed. In this way generalisations help people to can be applied more negotiate and understand the world they live in. broadly to related phenomena Inferences and observations An observation, in its purest form, is simply data that has no inherent meaning. However, all humans have a tendency to subconsciously view all new observations within the context of past experience, preconceived assumptions, available evidence and the collective understanding of those around us. This reasoning is used to make judgements about what is being observed. This in turn helps to make inferences about cause and effect, predict patterns, find trends in data and determine how things can be classified (Figure 4.1.2). Past experience All humans have past experiences that shape the way they interpret the world. For example, many people that experience arachnophobia have had a frightening experience with spiders in their youth, while other people that did not have the same frightening experience may react calmly to spiders. These differing past experiences can lead to people interpreting the presence of a spider in different ways. Preconceived assumptions 4.1.1 Preconceived We all have preconceived assumptions about what has happened and why. These assumptions often assumptions: A time lapse of a come in the form of inferences that have never been tested in the past and are used to inform another forest during a growing season inference. A common preconceived assumption in young children is that lighter objects will fall more slowly than heavier objects. They often do not take into account air resistance as opposing gravitational force. 78 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  It is not until this assumption is tested with objects of similar shape and size but INQUIRING FURTHER with a different mass that this assumption is abandoned. People sometimes think that lighter objects fall more slowly than heavier objects. Can you think of a Available evidence situation that would create the false assumption that The observations people make don’t always enable them to gather all the lighter objects fall more slowly than heavy ones? Design an investigation to test the assumption that available evidence. This may be due to a number of reasons; however, it generally mass influences the velocity of a falling object. includes issues of time, scale and available technology. For example, a plant that is observed for an hour will not appear to move or respond to a stimulus. mass However, if the same plant is observed over a week using time lapse photography, amount of matter in a solid, liquid or gas the ability of the plant to move and respond becomes readily apparent. Collective understanding The stories, experiences and knowledge of other people have the ability to influence the way we think 4.1.2 A about the things we observe. Humans are social animals, and the opinions and thoughts of others have palaeontologist discusses the the capacity to influence our reasoning. When we go to school, we learn about the discoveries of scientists relationship between birds like Charles Darwin and use his theory of evolution via natural selection to explain how modern birds and dinosaurs descended from dinosaurs. 4.1.3 Bird- like dinosaur Velociraptor 4.1.4 Bird-like FIGURE 4.1.2 To dinosaur make an informed Chirostenostes Observation inference scientists take into account their Available observations as well Past experience evidence as logical reasoning. Reasoning Collective Assumptions understanding Inference Making inferences from quantitative and qualitative observations quantitative data numerical values The type of observations we make can be broadly classified into two types. Quantitative data refer to collected as evidence during an investigation observations that can measured; they are typically represented numerically and have standard units (e.g. calculations, measurements) (e.g. temperature or distance). Qualitative data describe something in its entirety and are observations that may use words or images to categorise observations (e.g. mammals that can be identified as dogs). qualitative data descriptive data Scientists use both types of observations to make inferences about the phenomena they observe. collected as evidence during an investigation (e.g. INQUIRING images, observational FURTHER sentences) In the 1950s Solomon Asch developed a series of experiments to examine how others could influence the perceptions of his participants. One experiment involved a participant among a group of actors. He asked the group to compare and match the length of lines on a card. The actors all gave incorrect answers, and at first, the one ‘real’ participant gave the correct answer. As time went on, the participant elected to change their responses to match those of the actors. Research other experiments on conformity. What ethical considerations would need to be met to conduct a conformity 4.1.5 Asch conformity experiment today? What factor would influence the results? How can you check that the results are reliable? experiment 9780170411196 CHAPTER 4 » Cause and effect – inferences and generalisations 79  INVESTIGATION 4.1.1 Collecting quantitative and qualitative data Every experiment endeavours to collect data in one form or another. One of the major challenges for scientists is to decide what data needs to be collected to effectively answer their question. Collecting the right type of data will enable scientists to make and draw inferences with increasing validity. AIM To conduct a collaborative investigation that requires the collection of appropriate quantitative and/or qualitative data and analyse its validity An investigation may be chosen from one of the following questions. How do different variables such as temperature, light and soil pH affect the growth rate of plants? (pick one variable) How do variables such as surface area, temperature, speed of flow (stirring), acid volume and concentration influence the reaction rate of calcium carbonate in acid? (pick one variable) What variables, such as temperature, and continuous and non-continuous use, affect the life of a battery? (pick one variable) How do different variables such as turbidity, pH, oxygen saturation levels and nutrient load impact the water quality of a local pond or stream? (pick one variable) MATERIALS relevant equipment to perform and make quantitative and qualitative observations according to the selected investigation complete a risk assessment on any materials with an associated risk METHOD 1 In a team select a question on which to base the investigation. 2 Create an aim for the investigation. Mark Fergus Photography 3 Design a method for the investigation, being sure to include equipment, the type of data that will be collected and how it will be recorded. 4 Conduct the investigation and record the data. 5 Record the quantitative and/or qualitative observations. RESULTS Analyse the data and propose a number of inferences that could be made to explain or describe the observations. DISCUSSION 1 Quantitative and qualitative data have different characteristics. Identify the types of data collected in the investigation. 2 Justify why the investigation required the collection of the particular types of data identified in Question 1 in order to meet the aim. 3 Identify data that was not collected that could further increase the validity of the inferences. FIGURE 4.1.3 A vigorous reaction is produced 4 Select the inference that is most likely to explain or when marble chips (calcium carbonate) are added describe the phenomena in the investigation and to a high volume and concentration of hydrochloric acid. justify your reasoning. 80 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  Observations and inferences made by Aboriginal lore tradition and and Torres Strait Islander peoples knowledge held by a cultural group passed down through the The traditional lifestyle of Aboriginal and Torres Strait Islander peoples requires that they make close generations observations of Country and Place in order to survive. From these observations, Aboriginal and Torres leaching Strait Islander peoples are able to infer what plant foods are edible, when to collect and how to prepare process in which water- soluble substances them; how to find fresh drinking water; and when and where hunting and fishing will be most abundant. are dissolved into The inferences and generalisations about Country and Place are central to the culture of the Aboriginal surrounding water, allowing the substances and Torres Strait Islander peoples and are passed down from one generation to the next. to be transported and removed from their source material A toxic puzzle: Removing plant toxins species A number of edible Australian native plants species can pose a significant risk of poisoning if they are group of living organisms with similar incorrectly prepared. Determining the correct techniques requires close observation and reasoning characteristics that can to make the appropriate inferences regarding their preparation. The correct way to prepare these interbreed plants is a part of Aboriginal lore and the knowledge is kept according to the male or Getty Images/Photolibrary/Ted Mead female gender association of the plant. This means that either the men or the women are entrusted with the knowledge of how best to collect, prepare and cook particular plants, as well as their potential medicinal uses. Youth are often not entrusted with this knowledge until they have demonstrated responsible use and understanding of safer foods and materials. Some of the plants that require safe preparation via leaching include the following. Cunjevoi or Spoon Lily (Alocasia brisbanensis) is a rainforest plant found along the east coast of FIGURE 4.1.4 Cunjevoi (Alocasia brisbanensis) is a highly toxic plant. Australia. The plant, including its large starch-rich rhizome, is poisonous, and even a small amount incorrectly prepared has been known to kill. Records indicate that Indigenous peoples removed © M. Fagg, Australian National Botanic Gardens the toxins by soaking the rhizomes for an extended period of time in water to leach out the toxins, before pounding the rhizome and making it into cakes for roasting. Due to its highly toxic nature, Cunjevoi is not utilised as a food source today. Bracken (Pteridium esculentum) is a hardy fern that grows in forests, heaths and paddocks with a high to moderate rainfall. It is toxic to both humans and livestock due to its high tannin content and leucocyanidin. However, the new shoots and rhizome can be eaten if leached or boiled correctly. Nardoo (Marsilea mutica and Marsilea drummondii) are ferns with clover shaped leaves that grow in river flats and on the edges of swamps and wetlands throughout inland Australia. The sporocarps are separated from their casings and leached in water to remove the toxins. They are FIGURE 4.1.5 Nardoo (Marsilea drummondii) showing then ground and baked as cakes. Famously, the the sporocarps that are used to make cakes. 9780170411196 CHAPTER 4 » Cause and effect – inferences and generalisations 81  explorers Burke and Wills starved to death while eating nardoo cakes, possibly because they failed to prepare the sporocarps correctly to remove the enzyme thiaminase which depletes the body of vitamin B1. 4.1.6 Aboriginal exploitation of toxic nuts as a late-Holocene subsistence Wonky holes: Fresh water in the ocean strategy in Australia’s forests Wonky holes are submarine freshwater springs found along the Great Barrier Reef. They attract large numbers of fish and are thought to act as nurseries. They are of significant cultural importance for wonky hole submarine freshwater Indigenous peoples. spring found along the Great Barrier Reef INQUIRING FURTHER Contact your local Aboriginal or Torres Strait Islander community and arrange a field trip to explore the local environment. Investigate how Indigenous peoples in your local area used inferences and observations to know what 4.1.7 Submarine foods were edible, when to collect them and how to prepare them. Prepare a report for the class based on what you groundwater discovered during your investigation. discharge into the near-shore zone of the Great Barrier Reef 4.1.8 ‘Wonky holes’ help coastal water planning WS Worksheets Homework 4.1.1 Observations and inferences SECTION REVIEW REMEMBERING 1 Define and provide an example of an 4.1 a ‘observation’. b ‘inference’. UNDERSTANDING 2 Discuss the main idea behind making inferences in terms of scientific processes and developments. 3 Outline the relationship between observations, inferences and generalisations. APPLYING 4 Show how you would test a hypothesis based on an observation, inference and generalisation. Support your answer with an example from your own experience. 5 A person makes the claim that you can catch the flu by being exposed to cold weather. Identify the reasoning you would apply to challenge this person’s claim. Explain how you could support your reasoning. 6 Identify and discuss the types of observations and inferences Aboriginal and Torres Strait Islander peoples would traditionally have made to identify a poisonous plant. 7 Describe the observations and inferences that traditionally would have been made by Aboriginal and Torres Strait Islander peoples in order to recognise that leaching could remove the toxins from poisonous plants. ANALYSING 8 Conduct a secondary-sourced investigation into the characteristics of wonky holes and explain how the characteristics of these phenomena would have indicated the presence of fresh water to Aboriginal and Torres Strait Islander peoples. 82 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  4.2 Using secondary sources Informing your data with research Humans have been making observations and inferences about the natural With permission of University of Delaware Library Special Collections world since the birth of humankind. The ability to make accurate observations and sound inferences about the world around us is vital for survival. For much of human history the knowledge gained was transmitted by word of mouth which required direct contact between those with the knowledge and the learner. With the development of written language, direct contact between people was no longer needed, and it became possible for knowledge to be transmitted over large distances and time. The Greeks, who were recording their observations prior to 600 BCE, are known as being one of the first civilisations to document their findings on the natural world. By documenting their observations and their inferences they formed the foundations of scientific knowledge. For example, the scientist John Dalton (also known as the father of modern chemistry), was influenced by the FIGURE 4.2.1 A 1573 edition of one of the two surviving works of Democritus. This work most works of the ancient Greek philosopher Democritus in the development of likely influenced John Dalton, who is credited his model of the atom. In turn, Dalton’s model has been further developed by with being the father of modern chemistry. scientists such as Ernest Rutherford, Niels Bohr and Albert Einstein. Through consulting the writings and accumulated knowledge of those before them, scientists atom have been able to further develop an understanding and knowledge of the natural world. By utilising from the Greek word ‘atomos’ meaning recorded works scientists today have no need to start from the very beginning and can instead focus on cannot be divided contributing to the continued evolution of scientific knowledge. Consulting the research Consulting the research literature in the area of interest is vital before commencing a scientific investigation. research literature accumulated written By consulting secondary sources research scientists are able to capitalise on the accumulated knowledge knowledge based on and collective understanding of scientists before them and focus their efforts on areas that are not as well investigations and thoughts of scientists researched or understood. The advantages of consulting the research are outlined below and in Figure 4.2.2. that have been published Making inferences from the research All scientific investigations require evidence to support their findings. By reviewing the work of scientists working in the same or related fields a scientist can draw on the collective understanding and reasoning of the scientists that came before them. This means that scientists do not have to start at the very beginning but are instead able to further build on the research within the field and thus contribute to an ever expanding body of knowledge. For example, by consulting Democritus’ work Dalton was able to build on the idea that atoms were indivisible. Alternatively, scientists can challenge the reasoning underpinning the inferences drawn from observations in previous studies and go on to test them. This has the potential to establish an alternative interpretation of the evidence and overturn flawed conclusions. Develop inquiry questions The vast majority of scientific investigations begin with a question the researcher wishes to molecule answer. By consulting the research, a scientist is able to determine which questions have already group of atoms bonded together, representing been answered by other scientists and find gaps in the research where questions have not been the smallest fully answered or only partially answered. This can help a scientist focus on an area that is under fundamental unit of a chemical compound researched and make a more substantial contribution to the body of scientific knowledge. For that can take part in a example, Democritus was unable to explain how atoms formed what is now known as molecules. chemical reaction 9780170411196 CHAPTER 4 » Cause and effect – inferences and generalisations 83 hypothesis This question was of great interest to Dalton and other scientists, and could only be addressed as educated guess the understanding of the atom developed. tested through experimentation to answer the inquiry question; states the Construct suitable hypotheses relationship between A hypothesis is developed by making a proposition about how the independent variable and the the independent and dependent variables dependent variable relate to one another. By reviewing the research, a scientist can determine which independent variables and their relationships to other variables have been tested in the past, how these variables may variable relate to a potential inquiry question and which variables may not have been tested. This helps a scientist factor deliberately changed during an develop a hypothesis relevant to their own inquiry question. For example, using Democritus’ ideas and investigation to obtain the discovery of other elements Dalton was able to propose a hypothesis that atoms combined to form data molecules in whole number ratios. dependent variable factor measured in the investigation Plan suitable investigations inquiry question There are many ways to conduct an investigation on an inquiry question, and the methods and driving force of the research and can technology used can influence the reliability and validity of the results they obtain. Scientists can be investigated learn how other investigations similar to their own were conducted previously, and the types of scientifically tools and technology that were used by consulting the research. This may be of great assistance element in designing the method of their own investigation. For example, Dalton used or adapted many substance that cannot be separated into of the techniques employed by his fellow chemists to conduct his own investigations. Which smaller substance by chemical means techniques Dalton used often depended on the particular requirements of the investigation, and the equipment and technology he had available to him. WS Avoid unnecessary investigation Worksheets Homework There is a vast amount of research that has been done by scientists in the past and it is impossible 4.2.1 Using secondary for a single person to know of all the investigations that have been done before them. By consulting sources the research, scientists can determine which investigations have been conducted in the past and which have not. This reduces unnecessary repetition and will allow them to make a unique contribution to science. For example, To avoid unnecessary investigation by Dalton did not use his time needlessly trying seeing what to discover elements that had already been investigations have been conducted discovered. in the past To learn from the To make inferences Repeating investigations research methods of from the research other scientists by learning from An important aspect of science is that the to improve validity the work of research that is published is verified and and reliability other scientists Reasons accurate. Many scientists want to make a unique to consult research contribution to science by addressing an inquiry question that has never been asked before. However, it can be argued on ethical grounds that repeating research that has previously been To develop inquiry published is just as important as it confirms To construct questions by reliable research and challenges research that hypotheses to test determining variables that may has flaws. which questions have been identified have been answered in the research and which have not FIGURE 4.2.2 Five reasons to consult the research when commencing an investigation. 84 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  INVESTIGATION 4.2.1 Utilising secondary sources Collecting and reviewing information from secondary sources is an important component of conducting a scientific investigation. By doing so, scientists can source the different perspectives of various researchers and critically analyse the similarities and differences in their findings. AIM To review the similarities and differences in secondary sources based on Investigation 4.1.1 and explain how the findings are applicable to related scientific fields MATERIALS relevant secondary sources based on the chosen investigation METHOD 1 Select a range of secondary sources that address the following investigation initially selected in Investigation 4.1.1. (Note: five sources should be a minimum.) Secondary sources related to plant cell structures and size, and the development of measurement in microscopy Secondary sources related to calcium carbonate in acid and chemical reactions in cave formations Secondary sources related to factors affecting battery life and energy storage Secondary sources related to the impact of humans in a local environment and methods of environmental measurement 2 Collate the secondary source details such as Author, Date of publication, Title, Journal or Publisher name, or internet URL with date of access using the bibliography style of your school. 3 Summarise the findings of each secondary source. 4 Identify and outline incidences where the secondary sources provide similar or different information. RESULTS 1 Write a descriptive report on the theoretical findings of the various secondary sources and identify areas in which they are similar or different. 2 Create a glossary of specific concepts used in the secondary sources. DISCUSSION 1 Explain why it is important for the information in secondary sources to correlate in order to draw an inference about the data from the experiment. 2 Not all secondary sources will support the same explanation or method for the experiment. Identify what factors or influences could lead to the differences of opinion between the authors of the secondary sources. 3 Identify what information would be needed on a secondary source to establish the reliability and validity of the information it contained. 4 Describe the information contained in the secondary sources that gives an indication of the reliability and validity of the source. 5 Explain why it is important to evaluate the reliability and validity of secondary sources. 9780170411196 CHAPTER 4 » Cause and effect – inferences and generalisations 85  SECTION REVIEW REMEMBERING 1 Define and provide an example for: 4.2 a ‘secondary sources’. b ‘inquiry question’. c ‘hypothesis’. UNDERSTANDING 2 Describe three reasons to consult secondary sources in order to improve the quality and relevance of an investigation. 3 Explain how science has been able to build upon the knowledge and understanding of previous generations by utilising secondary sources of research. APPLYING 4 Explain how consulting the research may help you to develop a clear understanding of what you want to investigate and to identify a suitable inquiry question. 5 A student wished to investigate the inquiry question, ‘How does air pressure in a soccer ball affect how far it travels when the same force is applied?’ Referring to the inquiry question, create a list of terms to be searched to find relevant secondary sources and justify their inclusion on the list. 4.3 Observing patterns Patterns in data psychologically Humans are psychologically primed to recognise patterns. Deep in humanity’s evolutionary past, primed effect where exposure recognising patterns was essential to survival. Being able to recognise the patterns in animal tracks, to a particular stimulus the sudden flight of prey animals when they detect a predator and the seasons are all patterns that if unconsciously influences a person’s unrecognised could have cost early humans their life. response and Scientists also must be able to recognise patterns in data. Recognised patterns help to build a body of understanding of the stimuli evidence needed to support scientific conclusions in experiments. The theories, models and laws that are developed are then utilised to advance technology and society, and to make predictions into the future. For example, if an experiment was conducted to test the hypothesis, ‘The type of paper used in a paper plane can influence how far a paper plane will fly’, the results may show a pattern in which one type of paper causes the paper plane to fly further than another type under the same conditions. In this case, the pattern detected in the results confirms the hypothesis. type II error The failure to recognise a pattern when there is actually one present is called a type II error. Often this when a hypothesis is incorrectly rejected happens when a hypothesis is incorrectly rejected. For example, the above hypothesis may be rejected valid if the experimenter failed to notice that the wind had increased while conducting the experiment and extent to which a skewed the results so that it looked like the type of paper didn’t make a difference. report or investigation contains accurate Consequently, scientists expend considerable time and effort to ensure their experiments are both data, inferences and valid and reliable so they can correctly interpret the patterns in the experimental data. conclusions reliable extent to which an observation and/or Observing natural and universal patterns through time and space measurement can be repeated under the If a phenomenon happens right in front of a scientist as they observe it, it becomes relatively easy to same circumstances and produce similar results detect patterns in the data and formulate a hypothesis which can then be used to explain what caused the phenomenon to happen. However, it is much more difficult for a scientist to collect the data they need to support a hypothesis if that data spans considerable amounts of time, space or scale. To collect the data 86 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  themselves, a scientist would often need to travel significant distances, wait for developments in technology or need vast amounts of time: something the average scientist cannot achieve alone. As communication, record keeping and technology has improved, so too has the ability of science to explain phenomena that otherwise would have remained a mystery. By networking with other scientists and enthusiasts across the globe, checking historical records and keeping up with advances in technology, scientists working in similar areas are able to gather the data that establishes the patterns needed to support their hypotheses. Migrating Australian birds The regular appearance, disappearance and reappearance of birds according to the season suggests that they are migrating to the casual observer. Where they go often can remain a mystery. But when the birds migrating process of moving are caught and banded by a scientist a more complete picture of their migratory patterns can be built. from one region to Having a network of ornithologists around the globe ensures that migrating birds with bands attached can another according to the seasons be tracked and their location recorded so that a pattern soon emerges. Some birds like the Grey Fantail (Rhipidura albiscapa) will spend winter in Queensland and summer as far south as Tasmania, while others like Bar-tailed godwits (Limosa lapponica) make the journey to the mangroves and mudflats of South Australia in September before returning to Alaska and Siberia to breed for the northern summer (i.e. June, July and August). By having a large network of colleagues tracking the birds over the globe, scientists can 4.3.1 Where do bush birds go? determine the birds’ travel path and enable stopover points to be protected to ensure their survival. 4.3.2 Migratory birds make journey from BirdLife Australia Alaska to Adelaide for summer vacation FIGURE 4.3.1 The East Asian Australasian flyway. Halley’s Comet comet small celestial object While on a trip to Paris in 1680 Edmond Halley noted the position of a comet in the morning sky. At the composed primarily of dirt, gas and ice that time comets were thought to be unique one-off events, but then in 1682 another comet was seen in the travels on an elliptical skies over England. Halley’s curiosity was sparked and he endeavoured to plot the path of the comet, with (oval-shaped) path on its orbit around the Sun the help of Sir Isaac Newton’s theory that the Sun’s gravity affects the motion of planets and other celestial objects. Halley searched the historical records and was able to confirm three previous sightings of the comet, the most famous being on the Bayeux Tapestry which records the invasion of England by William the Conqueror in 1066. By taking previous observations of the comet and using Newton’s gravitational 4.3.3 A brief theory, Halley was able to determine that this comet had an elliptical path and that it should complete its history of Halley’s Comet 9780170411196 CHAPTER 4 » Cause and effect – inferences and generalisations 87  journey once every 75 years. Further historical research by other scientists has found records of Halley’s Comet that date as far back as China in 239 BCE, and Babylonia in 164 BCE and 87 CE. Halley’s Comet last made an appearance in 1985−6 and it is not expected to return until 2061. © Professor Steven Dutch Neptune Uranus Saturn Jupiter 2000 1995 1990 1989 2005 1988 2010 1987 2024 1986 2061 2040 2060 2045 2059 2050 2055 2056 2057 2058 FIGURE 4.3.2 Halley’s Comet on its current trajectory. Snowflakes The unique shape of snowflakes was a mystery that had long interested scientists; however, technological breakthroughs and developments in chemistry have helped to solve some of this mystery. Advances in microscopy enabled scientists to determine that there is a microscopic dust particle at the centre of every snowflake. Advances in weather monitoring technology found that if Science Photo Library/KENNETH LIBBRECH FIGURE 4.3.3 Hexagonal symmetry in a snowflake is FIGURE 4.3.4 Snowflake showing hexagonal symmetry caused by formed when water forms hydrogen bonds. the hydrogen bonds between the water molecules. 88 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  the dust particle is moving through air that is below 0° Celsius and has a water saturation between hexagonal 1.4–0.1 g/m3 a snowflake will form. The basic shape of the snowflake is dependent on the ratio symmetry repeating pattern that of temperature to water saturation of the air. Finally, advances in the understanding of chemistry forms a shape that can be cut into six identical explained that the polar nature of water molecules is caused by the distribution of the oxygen and wedges two hydrogen atoms which gives the molecule a positive and negative side that can form hydrogen fractal bonds. The snowflake’s fractal shape is the result of the hydrogen bonds that are formed when the mathematically related water molecules build up around the dust particle. This bonding forms the regular repeating pattern repeating pattern that exists at different of the crystal, typically with hexagonal symmetry, while the unique pattern of each snowflake is scales believed to be the result of variations in the original dust particle. In this way the beautiful fractal patterns of snowflakes form. INQUIRING 4.3.4 The FURTHER science of snowflakes In 1902, the Monthly Weather Review published several images of snowflakes. These images had been photographed by Wilson Bentley (1865–1931), a farmer whose hobby was photographing snowflakes under a microscope. Research the process Bentley used to collect and photograph snowflakes. Use your research to design a primary investigation to replicate Bentley’s. Groups in the periodic table In the early 19th century scientists were searching for a way to organise the elements that had been identified at the time. Then, in 1869, a Russian chemist named Dmitri Mendeleev (1834–1907) published the forerunner to the modern periodic table. He did it by creating groups periodic table organisational of elements with like properties, and demonstrating the resultant pattern called periodicity structure in which the that could be used to predict the properties of elements. atomic elements are arranged to highlight Mendeleev’s periodic table was so successful that the spaces he left in his table for undiscovered elements with similar elements were soon filled, with the newly discovered elements having many of the properties he predicted. properties Today the periodic table uses atomic number rather than weight as its means of organisation, and periodicity tendency to repeat at the noble gases have been added, but the fundamental structure of Mendeleev’s periodic table remains regular intervals unchanged. A major feature of the periodic table is the groups Mendeleev identified which run down electron the columns of the table. Increased understanding of the atom demonstrated that these groups have negatively charged elements of similar electron configurations. These configurations indicate that the elements in each particle in the atom spinning around the group have similar properties and behave in a similar chemical manner. For example, the alkali metals energy shells of the in group 1 have the characteristics of metals and tend to be very reactive while the noble gases in group atomic nucleus 18 exist primarily as gases and are unreactive. Scientists now use the periodic table to ‘see’ patterns in chemical reaction chemical process elements and predict the outcome of chemical reactions. that involves the rearrangement of the elements of the reactants into new products 4.3.5 Dimitri Medeleev: Chemistry’s improbable saviour 4.3.6 The genius of men 9780170411196 CHAPTER 4 » Cause and effect – inferences and generalisations 89  INVESTIGATION 4.3.1 Looking for patterns Not all observations and measurements allow a scientist to see an immediately obvious pattern. Sometimes it takes considerable time to gather enough data to be certain a pattern is there at all. However, once the data is collected it becomes possible to propose a hypothesis to explain the pattern that has been detected. AIM To examine data collected from observations and measurements on a given phenomenon, and determine if a pattern can be detected that can form the foundation of an explanatory hypothesis MATERIALS Select one of the following data sources. data collected from a phenomenon over time from an individual or personal investigation Internet sources providing data on the Aurora Australis or fractals in nature data of radioactive decay shown in Figure 4.3.5. FIGURE 4.3.5 Decay of erbium169 into thulium169 A graphical representation of 10 the data obtained by a physics student Amount of Tm169 who was monitoring 7.5 Mass (grams) the decay of the radioactive isotope erbium169 into the stable isotope 5 thulium169. 2.5 Amount of Er169 0 10 20 30 40 Time (days) METHOD 1 Carefully analyse the available data from your chosen source and determine if a pattern can be detected in the available data. 2 Note the pattern you have observed. RESULTS Propose a hypothesis that can be used to explain the pattern detected in the selected phenomena. DISCUSSION 1 Justify the reasoning for the hypothesis, with reference to the available data. 2 Describe the type of investigation that would need to be undertaken to confirm or reject the hypothesis that has been proposed. Include the dependent and independent variables, and any variables that would need to be controlled. 3 Predict what would happen to the pattern in the data if a variable in an experiment designed to test the hypothesis was not controlled. 4 Describe how failing to control the variable in question 3 would impact the decision to accept or reject the hypothesis. 90 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  Patterns that are not there All humans are capable of recognising patterns; however, sometimes a person detects a pattern that isn’t really there. Many common superstitions are examples of this, from the football star who always has to wear their lucky socks because they had a winning streak while wearing them in the past or the belief that people with cold hands have a warm heart. Yet in both of these cases there is no reliable and valid data to support the superstitious belief. Statistically, humans are far more likely to think there is a pattern where no pattern actually exists in comparison to thinking there is no pattern where there actually is one. Evolutionary psychologists theorise that this is because there is less risk associated with assuming there is a pattern when there isn’t one. For example, a person is not likely to lose their life if they cross their fingers for luck, but they may very well do so if they ignore the pattern that it is more likely a person will be hit by a car if they cross the road at a red pedestrian light. For this reason, seeing patterns that are not there tend to be far more common, ‘just in case’. In science these types of mistaken beliefs are known as type I errors. This can happen when a type I error when a hypothesis is proposed hypothesis is incorrectly accepted when it should not be. Often this happens when chance incorrectly accepted causes patterns to emerge in random data and because the human brain is primed to see patterns we assume that there is a pattern. Scientists go to considerable lengths to overcome this tendency using p-value statistical analysis, with the most common being the use of p-values. statistical measure of the probability of p-values give a statistical estimate of the likelihood that a scientist has made a type I error in the making a type I error analysis of their results. Typically, p-values under 5% are considered significant , whereas a p-value above 5% is considered insignificant. In statistical analysis the p-value is typically written as a percentage of 1; for example, p = 0.05 means that there is only a 5% likelihood that a type I error has been made. Pareidolia and optical illusions iStock.com/fotolinchen Pareidolia is the tendency to see faces in otherwise random objects or things and is one example of how the human brain is evolutionarily hardwired to detect patterns. Evolutionary psychologists theorise that pareidolia is a particularly common occurrence because from the moment we are born, humans are dependent on other humans around them. Being able to recognise faces and read facial expressions quickly is believed to have been advantageous in helping early humans socialise, as the stronger the social bond in a group the more likely the group was to survive, as each depended FIGURE 4.3.6 The face people can see in these on the others to aid in their survival. However, this predisposition can misfire clouds is an example of pareidolia. In reality, this and sometimes results in seeing faces that are not there. picture represents an image of water vapour, and light and shadow, yet the human brain will rarely Similarly, optical illusions can invoke the sense of seeing something that is fail to see the ‘face’ this image invokes. not really there. Optical illusions are the result of our brains taking ‘shortcuts’ in order to interpret information quickly. For example, Figures 4.3.7 and 4.3.8 pareidolia psychological priming show how the human brain can be tricked by perspectives that give the illusion of depth. Yet being able effect whereby a to judge depth quickly in a real life situation may mean the difference between life and death; for example, familiar pattern is perceived from random when determining how far away a deadly snake is. Take too long in those first few seconds to judge the stimuli distance and it may just result in a deadly bite. These shortcuts work because 99.9% of the time they judge distance accurately; it is only 0.1% of the time that they don’t (e.g. when presented with an optical optical illusion illusion). image that deceives the visual system Pareidolia and optical illusions are both examples of type I errors. Usually, they can be thought of as fun tricks of the brain; however, scientists need to be aware of how our brains are evolutionarily wired to perspective ensure they are not making snap judgements about the phenomena they are studying. By being aware of way of seeing or these brain shortcuts, scientists can work to overcome the innate biases they may have. interpreting something 9780170411196 CHAPTER 4 » Cause and effect – inferences and generalisations 91  Alamy Stock Photo/David BERTHO Alamy Stock Photo/David BERTHO 4.3.7 Pareidolia, seeing faces in strange places 4.3.8 Pareidolia: Why we see faces in hills, the moon and toasties 4.3.9 Objects are people too. The quirky world of facial pareidolia in pictures FIGURE 4.3.7 The viewing perspective of the image gives FIGURE 4.3.8 Viewed from another angle, the same image the illusion that the pyramid in front of the Louvre Museum can be shown for what it is; an optical illusion that plays on has disappeared. the brain’s tendency to take ‘shortcuts’ when judging depth. INQUIRING FURTHER Humans are exceptionally good at facial recognition. In just milliseconds a human can determine the age, gender and general features of a face in order to tell the difference between two or more faces. In contrast, computer software programmers have had to go to considerable length to ‘teach’ computers to recognise faces. Research the characteristics of human faces that computer software uses to determine the difference between one face and another. INQUIRING FURTHER The anchoring effect is a well-known psychological phenomenon where people tend to associate one number or fact to another unrelated number or fact. For example, 14.4% of people in Australia are over the age of 65. What is the maximum age of the youngest 50% of the Australian population? Most people will guess a maximum age somewhere between 40 and 50 years of age when the actual age is 34. The number 65 has acted as a mental anchor and swayed people to predict higher than they should. Other human psychological tendencies which result in misconception and errors are priming, the decoy effect, the illusion of scarcity, loss aversion and more. Which of these psychological tendencies are likely to create errors when analysing the results of an investigation? Data outliers Very rarely when conducting a scientific investigation will a scientist collect data that clearly shows a nice straight line relationship between the independent and dependent variables. It is more likely that the data points appear scattered across the graph. The scientist must then determine if the variables regression analysis can be related to each other in what is called a regression analysis. Typically, a regression analysis of two statistical process of establishing the variables that are related is known as a line of best fit. relationship between The closer the data points are to the line of best fit the greater the chances are that the variables are variables correlated; or in other words, there is a relationship between the variables. However, on occasion a data data outlier outlier can skew the line of best fit and reduce the confidence that the variables are correlated. In this data point distant from other observations and instance it is common to remove data outliers as it is likely that they occurred as a chance error. As a measurements that may result, a better correlation can be obtained. indicate an error The strength of a correlation in statistical analysis is typically represented by r and ranges from 0 to 1 correlation (though negative values from 0 to −1 can be found if the regression is negative; i.e. the line of best fit goes relationship or connection between two downward rather than upward). The amount of confidence that can be placed in a correlation is shown or more variables in Table 4.3.1. 92 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  TABLE 4.3.1 Correlations values and the confidence that there is a relationship between the independent and dependent variables. CORRELATION VALUE (r) CONFIDENCE r = 0 to 0.09 No confidence. No relationship exists between the variables. r = 0.1 to 0.29 Small confidence. It is very unlikely there is a relationship between the variables; random chance is just as likely to be influencing the results. r = 0.3 to 0.49 Medium confidence. A relationship between variable is suggested, though other unaccounted variables are likely to also be influencing the dependent variable. r = 0.5 to 1.0 Large confidence. A relationship between the variables is statistically very likely. Care must be taken when removing data outliers, as it can be tempting to remove data points that don’t ‘fit’ the pattern you hypothesised. The consequence is that data points are removed to suit the internal biases of the person conducting the data analysis and the result is that they create the pattern 4.3.10 Outliers: to drop or not they ‘want’ to see. If this analysis is then used to build a conclusion, its accuracy can be questioned. For to drop this reason outliers that are removed are often noted in the report. FIGURE 4.3.9 The © Laerd Statistics closer the data points are to the line of best r 5 0.4 r 5 0.7 fit the better the correlation. Removing a data outlier can change the position of the line of best fit and in turn improve the confidence in the correlation. Outlier Outlier removed WS Worksheets Homework 4.3.1 Observing patterns SECTION REMEMBERING REVIEW 1 Define ‘type I error’ and ’type II error’, and give an example of each. 2 Identify what the image in Figure 4.3.10 is an example of. 4.3 UNDERSTANDING 3 In 1912 Alfred Wegener proposed a hypothesis that the continents moved slowly over time due to changes in the Earth’s mantle; a hypothesis which was Shutterstock.com/dboystudio eventually accepted 40 years later as plate tectonics theory. The data needed to support this theory spans the Earth’s geological history. Explain why finding the data needed to establish the pattern that supports Wegener’s hypothesis was so difficult to collect. 4 Two students in Mr Lloyd’s Chemistry class were conducting an investigation on the rate of reaction. Vin proposed a hypothesis that increases in surface area of the reactants will increase the rate of reaction and conducted her investigation. The results gave a statistical p-value of 0.01. Bridgett proposed a hypothesis that increases in air pressure increased the rate of reaction and FIGURE 4.3.10 What do you see in this image? after conducting the investigation her statistical p-value was 0.2. Explain which investigation is likely to have the most reliable hypothesis. 9780170411196 CHAPTER 4 » Cause and effect – inferences and generalisations 93  APPLYING 5 Table 4.3.2 represents a random data sample collected by a student testing the relationship between how tall a girl is and her age. She is trying to establish what the average height is for girls according to age. Plot the data points on a graph and determine a line of best fit using all data points. Repeat the graph, this time removing data points that can be considered outliers. 6 Explain how the removal of outlier data points in question 5 changes the line of best fit (regression line) and can lead to greater confidence in the correlation between the age and height. TABLE 4.3.2 A random sample of girls by age and height in a high school. AGE AGE (TO NEAREST 6 MONTHS) HEIGHT (CM) (TO NEAREST 6 MONTHS) HEIGHT (CM) 11 136 13.5 170 11 146 14 166 11 148 14 170 11 151 14 161 11.5 151 14.5 172 11.5 155 14.5 175 12 150 15 170 12 155 15 172 12 159 15 173 12.5 154 15.5 172 12.5 160 15.5 174 12.5 164 16 174 13 150 16 176 13 162 16.5 172 13 168 16.5 182 13.5 164 17 173 13.5 168 17 176 Developing inquiry questions and 4.4 making generalisations Testing assumptions As discussed in section 4.1, one of the influences on the reasoning used to make an inference are the assumptions about what has happened and why. Often these assumptions are made without critically analysing their origin and how they influence a person’s thinking, yet they have the ability to bias the interpretation and analysis of the data in an investigation. The result can be a conclusion that is based false premise on a false premise. For this reason, scientists must be willing to examine their assumptions and seek incorrect proposition or assumption that is used alternative explanations through careful use of the scientific method and by reviewing related research to form the basis of an that other scientists have done previously in this area. By doing so scientists can gain new insight into argument or conclusion the phenomena to be investigated and be more confident their research is applicable in the real world. 94 MODULE TWO » Cause and effect – inferences and generalisations 9780170411196  INVESTIGATION 4.4.1 Overturning assumptions in history Throughout history, scientific assumptions have been overturned and rejected due to careful examination of the evidence. By challenging assumptions, scientists have been able to free the various scientific fields from flawed ideas that were holding them back from a more complete understanding of phenomena. AIM To examine long-standing false assumptions in a given scientific field and the investigations that overturned them through the use of secondary sources Fields to investigate include, but are not limited to: spontaneous generation and the investigations that led to the proposal of the germ theory Dalton’s proposition that atoms are indivisible and unchangeable, and the discovery of radioactivity (including the work of Henri Becquerel and Marie Curie) phlogiston theory and Lavoisier human influences on atmospheric pollution. MATERIALS Secondary sources reviewing historical examples of overturned assumptions, such as the internet sources listed below and associated weblinks. Pasteur brewing: Pasteur, beer and more 4.4.1 Experiments What is John Dalton’s atomic model? 4.4.2 What is John Dalton’s model? Benchmarks: Henri Becquerel discovers radioactivity on 26 February 1896 4.4.3 Benchmarks: Marie Curie: Unlikely revolutionary Henri Becquerel discovers Phlogiston theory radioactivity 4.4.4 Marie How do we know that humans are the major cause of global warming? Curie: unlikely revolutionary METHOD 4.4.5 Phlogiston theory Carefully analyse the available data for each overturned assumption from secondary sources and identify the 4.4.6 How do we following: know humans are the major cause of the initial assumption and its origin global warming? the scientist/s that debunked the assumption and the supporting evidence used to do so the implications this change in assumptions has had on the related field of study and any subsequent advances that have been made.