Stats

Power Calculations

R package Power Calculations

PWR2  tw0-way ANOVA

Usage ss.2way (a=a, b=b, alpha=alpha, beta=beta, f.A=NULL, f.B=NULL, delta.A=NULL, delta.B=NULL, sigma.A=NULL, sigma.B=NULL, B=B)

Arguments

a Number of groups in Factor A
b Number of groups in Factor B
alpha Significant level (Type I error probability)
beta Type II error probability (Power=1-beta)
f.A Effect size of Factor
A f.B Effect size of Factor B
delta.A The smallest difference among a groups in Factor
A delta.B The smallest difference among b groups in Factor B
sigma.A Standard deviation, i.e. square root of variance in Factor A sigma.B Standard deviation, i.e. square root of variance in Factor B
B Iteration times, default number is 100

NB

The effect size is just the standardised mean difference between the two groups.

Size effect =[ mean case – mean control] / standard deviation