Enter the mean and standard deviation of two separate groups of data. The calculator will display the Cohn’s D, also known as effective size, of the two data sets.

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- Confidence Interval Calculator (1 or 2 means)

## Cohen’s D Calculator

The following formula is used to calculate the effective size of two data sets.

Cd = (*M*_{2} – *M*_{1}) ⁄ *S*_{p}

*S*_{p}= √((*S*_{1}^{2} + *S*_{2}^{2}) ⁄ 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.

## FAQ

**What is 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.

**What is standard deviation?**

Standard deviation is average variation from the mean of a data set.