Scientific Methods PDF

The Scientific Methods Prof. Dr. Hala El-Haroun  What is Science? The goal of science is to investigate and understand the natural world. Scientists collect and organize information in a careful, orderly way, looking for patterns and connections between events. Scientists propose explanati...

The Scientific Methods Prof. Dr. Hala El-Haroun  What is Science? The goal of science is to investigate and understand the natural world. Scientists collect and organize information in a careful, orderly way, looking for patterns and connections between events. Scientists propose explanations that can be tested by examining evidence.  How is Science Done? Science begins with an observation. An observation is any use of the senses to gather information. Data is the information gathered from making observations.  Two Types of Data Quantitative Data Qualitative Data  Quantity  Quality  Numbers obtained by  Descriptions and either counting or characteristics that measuring cannot be counted  Example: A ball rolls  Example: The liquid 2 meters turned orange.  The Scientific Method The scientific method is a series of steps used by scientists to solve a problem or answer a question. The Steps to the Scientific Method 1. Ask a question 2. Form a hypothesis 3. Test the hypothesis (experiment) 4. Analyze the results 5. Draw conclusions 6. Communicate results  Ask a Question  What do you want to know or explain?  Use observations you have made to write a question that addresses the problem you want to investigate.  Example:  You walk into your house at night, turn on the light switch, but the light doesn’t turn on.  Why is the light not coming on?  Form a Hypothesis  What do you think will happen?  Predict the answer to your question or the outcome of the experiment  A hypothesis must be stated in a way that makes it testable  The hypothesis is just a possible answer to a question, and it must be thoroughly tested  The light will not turn on because the power is out.  Test the Hypothesis  Plan and carry out a controlled experiment  Only one variable is changed at a time  All other variables should be unchanged or “controlled”.  I will go to another room and turn on the light switch to see if the light will come on.  Control vs. Experimental Group An experiment is based on the comparison between a control group with an experimental group. Two groups are identical except for one factor The control group serves as the comparison It is the same as the experimental group, except that the one variable that is being tested is removed The experimental group shows the effect of the variable that is being tested  Independent vs. Dependent Variable The independent variable is the variable that is deliberately changed by the scientist. The dependent variable is the one observed during the experiment. The dependent variable is the data we collect during the experiment. This data is collected as a result of changing the independent variable.  Example In order to test the effectiveness of a new vaccine, 50 volunteers are selected and divided into two groups. One group will be the control group and the other will be the experimental group. Both groups are given a pill to take that is identical in size, shape, color and texture. Describe the control group. Group that doesn’t receive the vaccine. Describe the experimental group. Group that receives the vaccine. What variables are kept constant? The size, shape, color, and texture of the pill. What variable is being changed? Whether or not the pill contains the vaccine.  Example, continued. What was the independent variable? (What was changed?) It is the addition of the vaccine to the pills that were given to the volunteers. What was the dependent variable? (Effects?) The observed health of the people receiving the pills.  Analyze the Results  Scientists create tables and graphs to organize data and observations.  Does your data support your hypothesis? Hypothesis unsupported: You flip the light switch in the next room, and the light comes on. Hypothesis supported: You flip the light switch in the next room, and the light does not come on.  More on Analyzing  Is the data reliable?  Yes…  Draw a conclusion  No…  Is your data or experiment flawed?  Yes…  Modify the experiment to address the flaws in the original experiment  No…  Draw a conclusion  More on Analyzing  What are some reasons the data could be incorrect?  Light bulb is burnt out in both rooms, so the power really isn’t off.  How would you modify the experiment?  Turn on all light switches in the house.  It is OKAY if your hypothesis is proven wrong!!!  Draw a Conclusion  Write a conclusion that summarizes the important parts of your experiment and results.  Scientists must conclude whether their hypothesis was supported or not supported.  Repeat to check for errors or ask new questions.  The power is out in my house because I turned on two light switches in two different rooms and neither light turned on.  Communicate the Results  Scientists share what they have learned so others can repeat the investigation to see if they get the same results  Results can be published in scientific journals or reported during presentations  Theory vs. Hypothesis A theory may be formed after the hypothesis has been tested many times and is supported by much evidence. A theory is an explanation for a broad range of hypotheses and observations.