Question

How does the formula for Cohen’s d differ from a z-score?

Answer 1

Cohen's d is a measure of effect size.An effect size measures the magnitude of difference between groups.Effect size measures how something is effective than some other things.For example drug A is more effective than drug B.Cohen's D utilizes D (difference of groups means ) and pooled SD between groups.

Z-score is looks like Cohen's D but it is different.Main difference is Z score directly related to score instead of differences in groups. Z- score measures the significance between population mean of groups instead of of their effect on each other. Z score utilizes the standard error of groups.

formula , Cohen's d= mean1 - mean2/ square root of pooled sample variances

z score = mean2 - mean2/square root of sum of sample variances