Pooled Variance Calculator
Calculate pooled variance from two independent groups. Essential for two-sample t-tests assuming equal variances.
Enter Group Data
Example Data Sets:
Pooled Variance
22.355556
Pooled Std Dev
4.728166
Degrees of Freedom
9
Group 1 Statistics:
Sample Size (n1):
5
Mean:
17.4000
Variance:
15.800000
Sum of Squares:
63.2000
Group 2 Statistics:
Sample Size (n2):
6
Mean:
21.0000
Variance:
27.600000
Sum of Squares:
138.0000
Standard Error of Difference
2.863047
What is Pooled Variance?
Pooled variance is a weighted average of two or more sample variances, used when we assume the populations have equal variances (homoscedasticity). It provides a better estimate of the common population variance by combining information from multiple samples.
Pooled Variance Formula
Sp2 = [(n1-1)*s12 + (n2-1)*s22] / (n1 + n2 - 2)
Where n1, n2 are sample sizes and s12, s22 are sample variances.