What is effect size and how do I measure it?

What is effect size and how do I measure it?

Effect size is a quantitative measure of the magnitude of a phenomenon. It helps to understand the strength of a relationship or the size of a difference. You can measure it using various statistics like Cohen's d, Pearson's r, or odds ratios, depending on your data.

Can you explain Cohen's d and how to calculate it?

Cohen's d is a measure of effect size that indicates the standardized difference between two means. To calculate it, subtract the mean of one group from the mean of the other group, and then divide by the pooled standard deviation. The formula is: d = (M1 - M2) / SDpooled.

What does a Cohen's d value of 0.5 mean?

A Cohen's d value of 0.5 indicates a medium effect size, suggesting that there is a moderate difference between the two groups being compared.

Are there other effect size measures I should know about?

Yes, besides Cohen's d, you might want to explore Pearson's r for correlation, odds ratios for binary outcomes, and eta-squared for ANOVA. Each has its own context of use.