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Pooled Standard Deviation Calculator

Statistics
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Calculates the pooled standard deviation, an estimate of the standard deviation for two samples assuming equal variance, often used in two-sample t-tests.

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How To Use

How to use this calculator

Start with your values, or try a preset.

Step 1

Enter Sample 1 Size (n1), Sample 1 Standard Deviation (s1), Sample 2 Size (n2), and Sample 2 Standard Deviation (s2) in the units shown.

Step 2

Read Pooled Standard Deviation (sp) in the results panel. Results update as you change the inputs.

Step 3

Choose a preset to load an example, then adjust the values for your situation.

Worked Examples

Example calculations

See the inputs and their calculated results.

Small Samples

Sample 1 Size (n1): 10 ; Sample 1 Standard Deviation (s1): 5 ; Sample 2 Size (n2): 10 ; Sample 2 Standard Deviation (s2): 7

Pooled Standard Deviation (sp): 6.08276253

Unequal Sample Sizes

Sample 1 Size (n1): 10 ; Sample 1 Standard Deviation (s1): 5 ; Sample 2 Size (n2): 20 ; Sample 2 Standard Deviation (s2): 7

Pooled Standard Deviation (sp): 6.425396041

Similar Standard Deviations

Sample 1 Size (n1): 25 ; Sample 1 Standard Deviation (s1): 10 ; Sample 2 Size (n2): 25 ; Sample 2 Standard Deviation (s2): 11

Pooled Standard Deviation (sp): 10.51189802

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