Sample size for a test of a within-subjects mean linear contrast

Source: R/statpsych1.R

Computes the sample size required to test a linear contrast of population means with desired power in a within-subjects design. Set the average variance planning value to the largest value within a plausible range for a conservatively large sample size. Set the average correlation planning value to the smallest value within a plausible range for a conservatively large sample size.

size.test.lc.mean.ws(alpha, pow, var, es, cor, q)

Arguments

alpha

alpha level for hypothesis test

pow

desired power

var

planning value of average variance of measurements

es

planning value of linear contrast of means

cor

planning value of average correlation between measurements

q

vector of with-subjects contrast coefficients

Value

Returns the required sample size

Examples

q <- c(.5, .5, -.5, -.5)
size.test.lc.mean.ws(.05, .90, 50.7, 2, .8, q)
#>  Sample size
#>           29

# Should return:
# Sample size
#          29