Calculate the weighted average of standard deviations for two groups with different sample sizes.
Primary Group (G1)
Secondary Group (G2)
Statistical Analysis
Pooled Std. Deviation5.5227
Degrees of Freedom58n1 + n2 - 2
Pooled Variance30.5000
G1 Variance25.00
G2 Variance36.00
About this calculator
Overview
The pooled standard deviation is a method for estimating a single standard deviation to represent all industrial groups or samples when it is assumed that they come from populations with a common standard deviation.
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Pro Tips
Use this when you assume your two groups have homogeneous (equal) variances.
If an F-test shows significant variance differences, avoid pooling and use Welch's T-test instead.
The degrees of freedom for the pooled estimate is n1 + n2 - 2.
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Fun Facts
"Pooled standard deviation is a key component in the Student's T-Test for equal variances."
"It gives more weight to groups with larger sample sizes, as they are more 'reliable' estimators."
"If sample sizes are equal, the pooled variance is simply the average of the two sample variances."
