Welch's Unequal Variances Two-Sample t-Test

Use Welch’s independent two-sample t-test when population variances need not match. Calculate separate standard-error contributions, effective degrees of freedom and nonzero-null contrasts. Explore unequal sample sizes, variance pretests, allocation decisions, group transformations and the limits of unequal-variance protection. Prerequisites: one-sample t-tests and variance of independent means. The final algebraic bound is derived in the explanation. Includes single-select and multiselect practice with worked solutions and explanations of distractors.

References: 1.3.5.3 Independent t statistics, pooled variance, effective degrees of freedom and paired design, Details.