For a one sample z-test, Cohen’s d is a measure of the effect size of the test. It is calculated by using the following formula:
Cohen’s d : (x – µ) / σ
where x is the sample mean, µ is the population mean, and σ is the population standard deviation.
To find Cohen’s d for a given sample mean, population mean, and population standard deviation, simply enter the appropriate values in the boxes below and then click the “Calculate” button.
|Sample mean (x)|
|Population mean (µ)|
|Population standard deviation (σ)|
Rules of thumb for interpreting Cohen’s d :
d = 0.2 : small effect
d = 0.5 : medium effect
d = 0.8 : large effect