Lecture 09: Inference from Two Independent Samples

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Study design comes before the test

Difference between two population proportions

Testing equality: pooled standard error

Confidence intervals and a nonzero null difference

Drone-blade quality exercise

Exercise and falls: supplied worked example

Difference between two population means

Equal-variance t method

Concrete-temperature exercise

Welch’s t method: allow unequal variances

Tropical flowers: comparing the two t methods

Graphical evidence exercise

Rebar exercise and confounding

Bootstrap t inference for two means

Axial-stress exercise

Wilcoxon rank-sum / Mann–Whitney test

Exact distribution by hand