Enter the effect sizes and sample sizes of two groups into the calculator to determine the pooled effect size. This calculator helps in meta-analysis and systematic reviews to combine effect sizes from different studies.

Pooled Effect Size Formula

The following formula is used to calculate the pooled effect size.

d<sub>p</sub> = (d1 * (n1 - 1) + d2 * (n2 - 1)) / (n1 + n2 - 2)

Variables:

  • dp is the pooled effect size
  • d1 is the effect size of the first group
  • n1 is the sample size of the first group
  • d2 is the effect size of the second group
  • n2 is the sample size of the second group

To calculate the pooled effect size, multiply each group’s effect size by its sample size minus one, add these products together, and then divide by the total sample size minus two.

What is a Pooled Effect Size?

A pooled effect size is a statistical measure that combines the effect sizes from different studies to provide a single estimate of the effect. It is commonly used in meta-analysis and systematic reviews to synthesize research findings across multiple studies. The pooled effect size gives a weighted average of the effect sizes, taking into account the sample size of each study, which provides a more precise estimate of the overall effect.

How to Calculate Pooled Effect Size?

The following steps outline how to calculate the Pooled Effect Size.

  1. First, determine the effect size of the first group (d1).
  2. Next, determine the sample size of the first group (n1).
  3. Then, determine the effect size of the second group (d2).
  4. Next, determine the sample size of the second group (n2).
  5. Use the formula to calculate the pooled effect size (dp).
  6. Finally, calculate the Pooled Effect Size (dp).
  7. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Effect size of the first group (d1) = 0.5

Sample size of the first group (n1) = 100

Effect size of the second group (d2) = 0.7

Sample size of the second group (n2) = 150