size.ci.lc.mean.ws: Sample size for a within-subjects mean linear contrast...

In statpsych: Statistical Methods for Psychologists

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

Description

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

Usage

size.ci.lc.mean.ws(alpha, var, cor, w, q)

Arguments

alpha	alpha level for 1-alpha confidence
var	planning value of average variance of the measurements
cor	planning value of average correlation between measurements
w	desired confidence interval width
q	vector of within-subjects contrast coefficients

Value

Returns the required sample size

Examples

q <- c(.5, .5, -.5, -.5)
size.ci.lc.mean.ws(.05, 265, .8, 10, q)

# Should return:
# Sample size
#          11
 

statpsych documentation built on Sept. 11, 2024, 7:42 p.m.