Overview of the Day Research Methods Statistical Reasoning

What Characterizes Science? –The use of theory conceptual schemes for: –organizing scientific observations –organizing facts –generating hypotheses –Empiricism: confirming or falsifying theory –with data and facts –and using standard methods for collecting data

Why do we Need a Science of Psychology Limits of common sense and casual reasoning –overconfidence –hindsight Perceptual limitations Human nature is complex Increase our understanding of why we behave as we do and mechanisms underlying behavior

How do Scientists get Data? Scientific Method –controlled procedures that help to rule out other explanations

Variables Causal mechanisms and outcomes –independent variable (assumed cause) –dependent variable (assumed effect caused by independent variable) Example: –anxiety (IV) --> self-esteem (DV)

Types of Scientific Studies naturalistic observation correlational study field experiment laboratory experiment

Statistics What scientists use to: – summarize data –understand relationships between variables –estimate the probability of events occurring by chance –make inferences

Sampling Population –everyone or thing in a particular class Sample –a portion of people or things in a particular class Random sample –each person or thing has an equal probability of being included in a sample

Summarizing Data Graphs and Histograms (bar graphs) Measures of Central Tendency Measures of Variability Measures of Association

Graphs Visual display of data grouped by categories –example: the percentage of 3rd graders whose IQ scores fall within various intervals

Central Tendency Mean (the average) Median (score in the middle) Mode (most frequent score) Example: what is the mean, median, and mode of the following five heights: 60, 63, 63, 65, 67, 68, 69?

Variability Degree of dispersion around the middle –standard deviation Example 1: which sample would have the largest standard deviations in height? –a classroom of CMU students –all people in an elementary school Example 2: What would indicate the most consistency in free-throw performance (percentage made per game) in a season? a high or low standard deviation?

Degree of Association Correlation coefficient (-1.0, 0, +1.0) Degree to which two variables are associated with each other (does not imply causality) Examples: –height and weight –packs of cigarettes per day and incidents of lung cancer

Summary Science and scientific method Variables and types of scientific studies Statistics Sampling Summarizing data (graphs, central tendency, variability, association)