# Effect Size (Cohen’s D) for T-Test

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**Formula:**`d = (mean1 - mean2) / s`

## Introduction to Effect Size (Cohen’s D) for T-Test

Cohen’s D is a standardized measure of the difference between two means and is used to quantify the size of the effect in a T-Test. In the formula, ** d** represents the effect size,

**is the mean of the first group,**

*mean1***is the mean of the second group, and**

*mean2***is the pooled standard deviation of the two groups. A positive value indicates that the first mean is larger, and a negative value indicates that the second mean is larger. The magnitude represents the effect size relative to the standard deviation.**

*s*## Parameter usage:

`mean1`

= mean of the first group`mean2`

= mean of the second group`pooledStandardDeviation`

= pooled standard deviation of the two groups

## Output:

`d`

= effect size (Cohen’s D)

## Data validation

The pooled standard deviation should be greater than zero.

## Summary

This formula calculates the effect size (Cohen’s D) for a T-Test, providing a standardized measure of the difference between two means in relation to the pooled standard deviation. It is widely used in statistical analysis for evaluating the significance of findings.

Tags: Statistics, Effect Size, Test