Sample size for a between-subjects mean linear contrast confidence interval

Source: R/statpsych1.R

Computes the sample size in each group (assuming equal sample sizes) required to estimate a linear contrast of population means with desired confidence interval precision in a between-subjects design. Set the variance planning value to the largest value within a plausible range for a conservatively large sample size.

size.ci.lc.mean.bs(alpha, var, w, v)

Arguments

alpha

alpha level for 1-alpha confidence

var

planning value of average within-group variance

w

desired confidence interval width

v

vector of between-subjects contrast coefficients

Value

Returns the required sample size for each group

Examples

v <- c(.5, .5, -1)
size.ci.lc.mean.bs(.05, 5.62, 2.0, v)
#>  Sample size per group
#>                     34

# Should return:
# Sample size per group
#                    34