psych stats 3200*02

Observational vs Experimental Studies

Observational studies focus on either one person or a small group for specific reasons. This course is centered on experiments.

Inferential vs Descriptive Statistics

Inferential statistics allow for conclusions from a sample to a population. Key inferential tests include the z-test, t-test, ANOVA, and regression. Descriptive statistics summarize data, emphasizing mean, median, and mode as measures of central tendency.

Measures of Variance

Understanding population variance involves calculating the range (highest minus lowest), variance, and standard deviation, which show how populations differ.

Types of Variables

The two primary variables in experiments are independent (manipulated by the researcher) and dependent (measured outcome). Independent variables can be categorical (e.g., age groups) while dependent variables must yield numerical scores (e.g., ratings).

Scales of Measurement

Independent variables can be nominal (categorical, e.g., blood type) or ordinal (ranked, e.g., class year). Dependent variables can be interval (equal distances, less common) or ratio (absolute zero meaningful). Likert scales are treated as ratio data in psychology due to the optional non-response.

Data Representation

In data analysis, variables are represented by X (for scores) and Y (for secondary scores). Understanding how to manipulate these data points is crucial for subsequent statistical calculations, including finding sums and dealing with exponents.