PSYC 2019H Lecture 1 Winter 2021 Handout PDF

# PSYC 2019H - Lecture 1 ## Introduction and Basic Concepts - Basic Terminology - Introduction to Hypothesis Testing - Frequency Distributions - Shapes of Distributions ## Basic Terminology ### Descriptive Statistics "... organize, summarize, and communicate a group of numerical observations (N...

# PSYC 2019H - Lecture 1 ## Introduction and Basic Concepts - Basic Terminology - Introduction to Hypothesis Testing - Frequency Distributions - Shapes of Distributions ## Basic Terminology ### Descriptive Statistics "... organize, summarize, and communicate a group of numerical observations (Nolan & Heinzen, 2021, p. 3)." ### Inferential Statistics "... use sample data to make estimates about the larger population (Nolan & Heinzen, 2021, p. 3)." "The population includes all possible observations about which we would like to know something (N & H, 2021, p. 3)." A sample is a set of observations drawn from the population of interest (N & H, 2021, p. 3). ## Basic Terminology - Population: a group of all possible individuals or measurements of interest - Sample: a subset of the population that are selected to study - Study's Results: data collected during the study, this data is gathered from the sample ### Do older adults sleep less than younger adults? | Descriptive Statistics | Younger (n = 24) | Older (n = 24) | |---|---|---| | Mean (min.) | 472.88 | 391.42 | | SD | 70.42 | 72.29 | **Inferential Statistics** The total sleep time for older adults was significantly less than for younger adults, t(46) = 3.95, p < .001. - We would like to say this applies to ALL young and older adults - But, we need to be careful about the extent to which we generalize from our sample ## Basic Terminology ### Variable "... observations of physical, attitudinal, and behavioural characteristics that can take on different values (N & H, 2021, p.4)." ### Discrete Observations "... can take on only specific values (e.g., whole numbers); no other values can exist between these numbers (N & H, 2021, p.4)." ### Continuous Observations "... can take on a full range of values (numbers out to several decimal places); an infinite number of potential values exist (N & H, 2021, p.4)." ### Table 1-1 | Variable | Discrete | Continuous | |---|---|---| | Nominal | Always | Never | | Ordinal | Always | Never | | Interval | Sometimes | Sometimes | | Ratio | Seldom | Often | _Researchers can use four types of variables to quantify their observations. Two of them, nominal and ordinal, are always discrete. Interval variables can be discrete or continuous; ratio variables are almost always continuous. (Interval variables and ratio variables are often referred to as “scale variables.")_ ## Basic Terminology ### Nominal Variables "... used for observations that have categories or names as their values (N & H, 2021, p.5)." ### Ordinal Variable "... used for observations that have rankings (i.e., 1st, 2nd, 3rd,...) as their values (N & H, 2021, p.5)." **2006 Winter Olympics: Women's 5000-meter Speed Skating Results** | Athlete | Country | Time (min) | Difference (sec) | Rank | |---|---|---|---|---| | Clara Hughes | Canada | 6:59.07 | 1 (Gold) | | Claudia Pechstein | Germany | 7:00.08 | 1.01 | 2 (Silver) | | Cindy Klassen | Canada | 7:00.57 | 1.50 | 3 (Bronze) | | Martina Sablikova | Czech Republic | 7:01.38 | 2.31 | 4 | | Daniela Anschütz-Thoms | Germany | 7:02.82 | 3.75 | 5 | ## Basic Terminology ### Interval Variable "... used for observations that have numbers as their values; the distance (or interval) between pairs of consecutive numbers is assumed to be equal (N & H, 2021, p.5)." ### Ratio Variable "... a variable that meets the criteria for an interval variable but also has a meaningful zero point (N & H, 2021, p.5)." ### Scale Variable "... a variable that meets the criteria for an interval variable or a ratio variable (N & H, 2021, p.6)." ## Basic Terminology ### Independent Variable "... has at least two levels that we either manipulate or observe to determine its effect on the dependent variable (N & H, 2021, p.7)." ### Dependent Variable "... the outcome variable that we hypothesize to be related to or caused by changes in the independent variable (N & H, 2021, p.7)." ## Basic Terminology ### Confounding Variable "... any variable that systematically varies with the independent variable so that we cannot logically determine which variable is at work (N & H, 2021, p.7)." **TABLE 5.1 Confounding in a Hypothetical Distribution of Practice Experiment** | | Monday | Tuesday | Wednesday | Thursday | Friday | |---|---|---|---|---|---| | Group 1 | 3 | - | - | - | Exam | | Group 2 | 3 | 3 | - | - | Exam | | Group 3 | 3 | 3 | 3 | - | Exam | _Note: The 3 in each equals the number of hours spent studying five chapters of a general psychology text._ Goodwin and Goodwin (2017) ## Basic Terminology ### Reliability "... refers to the consistency of a measure (N & H, 2021, p.8)." ### Validity "... refers to the extent to which a test actually measures what it was intended to measure (N & H, 2021, p.8)." ## Introduction to Hypothesis Testing ### Hypothesis Testing "... the process of drawing conclusions about whether a particular relation between variables is supported by the evidence (N & H, 2021, p.10)." ### Operational Definition "... specifies the operations or procedures used to measure or manipulate a variable (N & H, 2021, p.10)." ## Introduction to Hypothesis Testing **Example: You are a researcher who studies infant health** - Does exercise during pregnancy help newborn health? - You send surveys to 1000 pregnant women - You find a statistically significant positive correlation between exercise and health indicators in newborns - Women who exercised more tend to have healthier infants ## Introduction to Hypothesis Testing ### Correlational Studies Correlation: "... an association between two or more variables (N & H, 2021, p. 11)." - Do not allow causal statements to be made - Potential confounding variables ## Introduction to Hypothesis Testing **Example: You are a researcher who studies infant health** - Does exercise during pregnancy help newborn health? - Can we study this 'better'? - Experiment: "... a study in which participants are randomly assigned to a condition or a level or one or more independent variables (N & H, 2021, p. 12)." - Random Assignment: “... every participant has equal chance of being assigned to any of the groups or conditions (N & H, 2021, p. 12).” ## Introduction to Hypothesis Testing **Example: You are a researcher who studies infant health** - Does exercise during pregnancy help newborn health? Pregnant women who wish to participate in your study ## Introduction to Hypothesis Testing ### Between-Groups Design "... an experiment is which participants experience one and only one level of the independent variable (N & H, 2021, p.14)." ### Within Design "... an experiment in which all participants in the study experience the different levels of the independent variable (N & H, 2021, p.14)." ## Introduction to Data Ethics ### Open Science "... an approach to research that encourages collaboration, and includes the sharing of research methodology, data, and statistical analyses in ways that allow others to question and even to try to recreate findings (N & H, 2021, p.15)." ## Introduction to Data Ethics ### Preregistration "... a recommended open science practice in which researchers outline their research design and analysis plan before completing a study (N & H, 2021, p.16)." - Example of a preregistered review plan - Open Science website ### HARKing - Hypothesizing After the Results are Known ## Frequency Distributions ### Raw score "... a data point that has not yet been transformed or analyzed (N & H, 2021, p.31)." ### Frequency distribution "... describes the pattern of a set of numbers by displaying a count or proportion for each possible value of a variable (N & H, 2021, p.31)." - Frequency Table - Grouped Frequency Table - Histogram ## Frequency Distributions ### Frequency Table "... a visual depiction of data, which shows how often each value occurred – that is, how many scores were at each value. Values are listed in the in the first column, and the number of individuals with scores at that value are listed in the second column (N & H, 2021, p.33)." ## Frequency Distributions ### Table 2-3. Volcanos Around the World | Country | Number | Country | Number | Country | Number | Country | Number | |---|---|---|---|---|---|---| | Antarctica | 1 | DRC | 2 | Italy | 6 | Portugal | 3 | | Argentina | 1 | Ecuador | 12 | Japan | 40 | Russia | 55 | | Australia | 4 | El Salvador | 5 | Kenya | 7 | Solomon Islands | 2 | | Azores | 3 | Eritrea | 2 | Lesser Sunda Islands | 1 | Spain | 5 | | Cameroon | 2 | Ethiopia | 10 | Libya | 1 | St. Kitts and Nevis | 2 | | Canary Islands | 1 | France | 4 | Mariana Islands | 4 | St. Vincent | 1 | | Cape Verde Islands | 2 | Galápagos Islands | 1 | Mexico | 7 | Tanzania | 3 | | Chad | 1 | Greece | 5 | Netherlands | 2 | Tonga | 1 | | Chile | 10 | Grenada | 1 | New Zealand | 8 | Turkey | 2 | | China | 1 | Guatemala | 7 | Nicaragua | 9 | Uganda | 1 | | Colombia | 3 | Iceland | 5 | Norway | 1 | United Kingdom | 4 | | Comoros | 1 | India | 2 | Papua New Guinea | 17 | United States | 81 | | Congo | 2 | Indonesia | 45 | Peru | 2 | Vanuatu | 9 | | Costa Rica | 4 | Iran | 2 | Philippines | 13 | | | *Four outliers: Indonesia (45), Japan (40), Russia (55), and the US (81)* ## Frequency Distributions ### Table 2-5. Frequencies and Percentages For Volcanos Per Country | Number of Volcanoes | Frequency | Percentage | |---|---|---| | 17 | 1 | 1.96 | | 16 | 0 | 0 | | 15 | 0 | 0 | | 14 | 0 | 0 | | 13 | 1 | 1.96 | | 12 | 1 | 1.96 | | 11 | 0 | 0 | | 10 | 2 | 3.92 | | 9 | 2 | 3.92 | | 8 | 1 | 1.96 | | 7 | 3 | 5.88 | | 6 | 1 | 1.96 | | 5 | 4 | 7.84 | | 4 | 5 | 9.8 | | 3 | 4 | 7.84 | | 2 | 12 | 23.53 | | 1 | 14 | 27.45 | Removed the four outliers: Indonesia (45), Japan (40), Russia (55), and the US (81) ## Frequency Distributions ### Grouped Frequency Table "... a visual depiction of data that reports frequencies within a given interval rather than the frequencies for a specific value (N & H, 2021, p.33)." ### Table 2-6. Grouped Frequency Table of Number of Volcanoes Per Country Around the World | Interval | Frequency | |---|---| | 80-89 | 1 | | 70-79 | 0 | | 60-69 | 0 | | 50-59 | 1 | | 40-49 | 2 | | 30-39 | 0 | | 20-29 | 0 | | 10-19 | 5 | | 0-9 | 46 | ## Frequency Distributions ### Histogram "... a graph that looks like a bar graph but depicts just one variable, usually based on scale data with the values of the variable on the x-axis and the frequencies on the y-axis (N & H, 2021, p.38)." This image depicts a histogram with the number of Volcanoes on the x-axis and Frequency on the y-axis. The Frequency on the y-axis ranges from 0 to 16. The Number of Volcanoes on the x-axis ranges from 0 to 17 ## Shapes of Distributions ### Normal Distribution "... a specific frequency distribution that is a bell shaped, symmetric, and unimodal curve (N & H, 2021, p.42)." This image depicts a normal distribution curve with the mean centered at 100. ## Shapes of Distributions ### Skewed Distribution "... a distribution in which one of the tails of the distribution is pulled away from the center (N & H, 2021, p.42)." This image is divided into two parts: (a) Positive skew and (b) Negative skew. Both images show a distribution curve, where the curve is skewed. ## The images in this document are intended to be described and not included, therefore I have described them in detail.