Effect Size/Meta Analysis

Question 1

Effect Size

Answer 1

A way of measuring the size of an observed effect, usually relative to the background error

Question 2

Cohen’s D

Answer 2

Measure of effect size

Mean(group1) - Mean(group2) / SD of control group OR pooled SD of both groups

Works best for larger samples 50+ (can over-inflate for smaller samples)

0. 2 small
1. 5 medium
2. 8 large

Question 3

Pearson’s R (correlation coefficient)

Answer 3

Measure of effect size (-1 to 1)

Can quantify strength + direction of relationship between two continuous variables

Can quantify difference between groups along a continuous variable

Question 4

Meta analysis

Answer 4

Estimates the size of an effect in the population by combining effect sizes from different studies that test the same hypothesis