size.ci.lc.prop.bs {statpsych} | R Documentation |
Computes the sample size in each group (assuming equal sample sizes) required to estimate a linear contrast of proportions with desired confidence interval precision in a between-subjects design. Set the proportion planning values to .5 for a conservatively large sample size.
size.ci.lc.prop.bs(alpha, p, w, v)
alpha |
alpha level for 1-alpha confidence |
p |
vector of proportion planning values |
w |
desired confidence interval width |
v |
vector of between-subjects contrast coefficients |
Returns the required sample size per group
p <- c(.25, .30, .50, .50) v <- c(.5, .5, -.5, -.5) size.ci.lc.prop.bs(.05, p, .2, v) # Should return: # Sample size per group # [1,] 87