What is the difference between effect size and p-value?

What is the difference between effect size and p-value?

Effect size measures the magnitude of a relationship or difference, while p-value indicates the probability of observing the data if the null hypothesis is true.

Can you give me an example of effect size?

Sure! In a study comparing two groups, if the mean difference in scores is 5 and the standard deviation is 10, the effect size (Cohen's d) would be 0.5.

And how do I interpret a p-value?

A p-value tells you the likelihood of obtaining your results if the null hypothesis is true. A p-value less than 0.05 typically indicates statistical significance.

So, can both be used together?

Yes, they complement each other. While p-value shows if an effect exists, effect size quantifies how large that effect is.