Psychological Research and Statistics Flashcards

A researcher finds p = 0.03 with a small effect size (d = 0.15). What is the most accurate interpretation?

Answer: The result is statistically significant but may lack practical significance

Statistical significance (p < 0.05) does not guarantee practical importance; a tiny effect in a large sample can be significant yet trivial.

Which sampling method divides the population into subgroups and randomly samples from each in proportion to their size?

Answer: Stratified random sampling

Stratified random sampling ensures proportional representation of subgroups by randomly selecting from each stratum.

In a 2×3 factorial ANOVA, how many main effects and interactions are tested?

Answer: 2 main effects and 1 interaction

A 2×3 factorial ANOVA tests two main effects (one per factor) and one two-way interaction.

What does a 95% confidence interval represent?

Answer: If repeated sampling were done, 95% of such intervals would capture the true parameter

A confidence interval is a frequentist statement about the long-run behavior of the procedure, not the probability for a single interval.

Which threat to internal validity occurs when participants are tested multiple times and improve due to familiarity with the test?

Answer: Testing effect

The testing effect (also called practice effect) occurs when repeated exposure to the same measure improves scores independent of the treatment.

A Pearson r = –0.72 between stress and immune function means:

Answer: Higher stress is associated with lower immune function

Correlation indicates the direction and strength of association but does not establish causation.

Power analysis is used in research planning primarily to:

Answer: Estimate the required sample size to detect an effect of a given size

A priori power analysis uses expected effect size, alpha, and desired power (typically 0.80) to determine the minimum sample size needed.