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

Cohen’s D Calculator

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

Cd = (M2 - M1) ⁄ Sp
Sp= √((S1^2 + S2^2) ⁄ 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 a statistical measure used to quantify the effect size of the difference between two groups. It indicates the standardized difference between the means of two groups, considering the variability within each group.

Cohen’s d is valuable as it allows researchers to determine the magnitude of an effect beyond statistical significance, providing a meaningful understanding of the practical significance.

Cohen’s d is important because it helps researchers interpret the practical significance of their findings. Statistical significance alone merely indicates whether the observed difference between two groups is likely to have occurred by chance or not.

By calculating Cohen’s d, researchers can determine the extent to which a difference exists between groups.

A larger Cohen’s d value indicates a more substantial effect size, suggesting a greater practical significance.

Cohen’s D Example

How to calculate Cohen’s D

  1. First, determine the means

    Calculate the means of each data set using a standard formula averages.

  2. Next, determine the standard deviations

    Calculate the standard deviations, s1 and s2, of each data set.

  3. Calculate the pooled standard deviation

    Using s1 and s2, calculate the pooled standard deviation of the set.

  4. 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 the average variation from the mean of a data set.