Reasoning in Psychology Using Statistics Psychology 138 2017

Reasoning in Psychology Using Statistics Psychology 138 2017

"There are three kinds of lies: lies, damned lies, and statistics. ” Mark Twain “Statistics have a bad reputation. We suspect that statistics may be wrong, that people who use statistics may be "lying" -- trying to manipulate us by using numbers to somehow distort the truth. Yet, at the same time, we need statistics; we depend upon them to summarize and clarify the nature of our complex society. This is particularly true when we talk about social problems. ” Telling the Truth About Damned Lies and Statistics, Joel Best (2001) • Scientific reasoning in psychology – improve your ability conduct and consume psychological research • Statistical Literacy – the ability to follow and understand arguments from data Course objectives Reasoning in Psychology Using Statistics

“It’s about almost everything in modern society. ” Bennett, Briggs, Triola (2003), Statistical Reasoning for Everyday life • Statistics are tools, used to make decisions based on data – Descriptive statistics – Inferential statistics • Data are numbers with a context – How were the numbers measured, what do they mean? What are Statistics? Reasoning in Psychology Using Statistics

• Main points from the video – Every statistical test starts with an appropriate selection of subjects – Inferences must be based on more than one observation because of variability – Two types of error must be controlled while testing hypotheses – A decision is based on two things: • The difference between groups • The variability of the scores Video review Reasoning in Psychology Using Statistics • Inferential statistics: hypothesis testing – rats, robots, and roller skates Wiley (1977)

• Scientific Method Producing Data Describing Data Conclusions from Data – Ask the research question – Identify variables and formulate the hypothesis – Define your population – Select a research methodology – Collect your data from a sample – Analyze your data – Draw conclusions based on your data – Repeat The research process Reasoning in Psychology Using Statistics

• Methodological basics: what are data and how they are produced – Research methods – Sampling • Observation methods • Experimental methods • Quasi-experimental – Variables • Types • Operational definitions – Measurements • Continuous and discrete • Scales of measurement • Samples and populations • Statistics and parameters • Techniques – – Basic Probability Experimental control Reliability Validity Producing Data Reasoning in Psychology Using Statistics • Internal and external • Confounds & Bias

• Descriptive Statistics: Statistical tools/procedures to help organize, summarize, and simplify large sets of data (distributions) – Describing a single distribution • Tables and Graphs • Properties – Shape, Center, Spread • Locating scores & Transforming distributions (z-scores) – The Normal distribution (Unit Normal Table) – Describing the relationship between 2 distributions • Correlation (Pearson’s r) Describing data Reasoning in Psychology Using Statistics

• Inferential Statistics: Procedures which allow us to make claims about the population based on sample data – Distribution of sample means – Hypothesis testing • Central Limit Theorem • Standard error – Error types • Type 1 (α) • Type 2 (β) • • • 1 -sample z test 1 -sample t test Related samples t-test Independent samples t-test Chi-squared test Correlation and regression – Estimation • Point estimates • Confidence intervals Conclusions from Data Reasoning in Psychology Using Statistics