📊F-test (Variance Ratio)
The F-test for equality of variances tests whether two populations have the same variance. F = s₁²/s₂² (larger variance in numerator). Used as a preliminary test before pooled t-tests.
- 1F = larger variance / smaller variance
- 2df₁ = n₁−1 · df₂ = n₂−1
- 3Compare to critical value from F-distribution
- 4F=1 means equal variances
s₁=2.5 (n=10) · s₂=1.8 (n=12)=F = 1.93 · df(9,11) · not significantVariances not significantly different
References
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