Magnitude of effect size, t

Taken from Wellek (2003) Table 1.1(v) and page 164

Setting

Parameter

Reference Value

Strict t

Liberal t

Sign Test

P(difference>0)

1/2

0.10

0.20

Mann Whitney

P[X>Y]

1/2

0.10

0.20

2 Binomials

Log $$\frac{p_text{1}(1-p_text{2})}{(1-p_text{1})p_text{2}}

0

0.41

0.85

Paired t

$$\frac{\mbox{Paired difference}}{\mbox{sd(difference)}}$$

0

0.25

0.50

Unpaired t

$$\frac{\mbox{Group mean diff}}{\mbox{average group sd}}$$

0

0.36

0.74

One-way ANOVA

[eta2 (N-k)][(1-eta2 ) mean(N)]

0

0.25

0.50

where mean(N) is the average group size