Diagrammatic Summary of Two sample Tests

Independent (unrelated) Samples

Paired related) Samples

NormalPopulation

Non-NormalPopulation

NormalPopulation

Non-Normal Population

12, 2

2 known 2

22

1

21

2121 )()(

nn

xxZ

12, 2

2 unknown

21

2121

11)()(

nnS

xxt

p

Mann-Whitney Rank Sum Test

nsd

td

)( 21

Two-Sample Sign TestWilcoxon Signed Rank Test