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Hedges g Effect Size Calculator

Hedges g Effect Size Calculator helps with statistics, diagnostics and similarity scores. Use Group mean difference, Pooled standard deviation, Total sample size to estimate g rather than relying on a fixed rule of thumb. This calculator uses the relationship difference/pooled*(1-3/(4*total-9)). Uses a common large-sample correction with pooled SD, not a significance test. It runs locally in your browser, so the values can be changed to explore a different scenario without transmitting the entered numbers to an external calculation service.

How to use this calculator

  1. Check the measurements for Group mean difference, Pooled standard deviation, Total sample size. Each field displays its input unit; do not mix cm, m, seconds or minutes.
  2. Enter the quantities for your own statistics, diagnostics and similarity scores scenario. Use ungrouped numeric values, with a period for decimals.
  3. Read the result in g and compare the underlying formula with your real situation. Uses a common large-sample correction with pooled SD, not a significance test.

How the Hedges g Effect Size Calculator works

Result in g = difference/pooled*(1-3/(4*total-9)). Inputs are expressed in the units shown in their labels.

  • The output uses the current values of Group mean difference, Pooled standard deviation, Total sample size, with no live service data, manufacturer information or personal information. This is a model, not a real-time measurement.
  • The tool rejects blank, nonnumeric and out-of-range inputs instead of displaying a misleading result. Uses a common large-sample correction with pooled SD, not a significance test. Review quantities, precision and units before using the result for a purchase, plan or technical choice.

Worked examples

Worked example: Hedges g Effect Size Calculator

Suppose Group mean difference = 6, Pooled standard deviation = 12, Total sample size = 60. The calculator processes these numeric quantities using its defined relationship.

Apply difference/pooled*(1-3/(4*total-9)) to those inputs, preserving the unit conversions in the expression.

Calculated value: approximately 0.4935065 g.

Understanding the result

The default example gives approximately 0.4935065 g; this is a mathematical output based on the example inputs, not a forecast of actual observed conditions.

Uses a common large-sample correction with pooled SD, not a significance test.

Important notes

Uses a common large-sample correction with pooled SD, not a significance test.

For a production decision, check the source measurements and local requirements before trusting this g estimate. The tool rejects blank, nonnumeric and out-of-range inputs instead of displaying a misleading result.

Frequently asked questions

What is the Hedges g Effect Size Calculator used for?

It converts Group mean difference, Pooled standard deviation, Total sample size into a calculated quantity in g, using the formula displayed above.

What assumptions matter for this calculator?

Uses a common large-sample correction with pooled SD, not a significance test. The outcome changes when measurements, operating conditions or units differ.

How do I verify a result from the Hedges g Effect Size Calculator?

Recalculate the worked example independently, check your units, and use measured data when available. The tool rejects blank, nonnumeric and out-of-range inputs instead of displaying a misleading result.

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Related explanations

Learn the method behind the number or compare the terminology before using the calculator.

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This page provides a calculation tool plus explanatory information so you can understand what the result means and when the underlying method may not fit your situation.