Enter the mean and standard deviation of two separate groups of data. The calculator will display the Cohn’s D, also known as effect size, of the two data sets.
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Cohen’s D Calculator
The following formula is used to calculate the effective size of two data sets.
Cd = (M2 – M1) ⁄ Sp
Sp= √((S12 + S22) ⁄ 2)
- Where Cd is cohen’s D
- M2 and M1 are the means
- S1 and S2 are the standard deviations
- Sp is the pooled standard deviation
Cohen’s D Definition
Cohen’s D is the proper effective size measure of two groups of data.
Cohen’s D Example
How to calculate Cohen’s D
- First, determine the means
Calculate the means of each data set using a standard formula averages.
- Next, determine the standard deviations
Calculate the standard deviations, s1 and s2, of each data set.
- Calculate the pooled standard deviation
Using s1 and s2, calculate the pooled standard deviation of the set.
- Finally, calculate Cohen’s D
Using the means from step 1 and the pooled standard deviation, calculate the Cohen’s d.
Cohen’s D is the correct effective size measure of two groups of data with similar standard deviations and the same size.
Standard deviation is the average variation from the mean of a data set.