Work out pooled standard deviation instantly with clear inputs, formula shown and shareable results.
Pooling combines two sample variances into a single estimate, weighting each by its degrees of freedom. It assumes the two populations share a common variance, which is the key assumption of the standard two-sample t-test.
Pooled variance
s²ₚ = [(n₁−1)s₁² + (n₂−1)s₂²] / (n₁ + n₂ − 2)
Standard error
SE = sₚ√(1/n₁ + 1/n₂)
The pooled standard deviation is about 1.4223 on 9 degrees of freedom.
Do not pool. Use Welch's t-test, which estimates the standard error without assuming equal variances.