size.ci.ratio.mean.ps {statpsych}

Sample size for a paired-samples mean ratio confidence interval

Description

Computes the sample size required to estimate a ratio of population means with desired confidence interval precision in a paired-samples design. Set the correlation planning value to the smallest value within a plausible range for a conservatively large sample size. This function requires planning values for each mean and the sample size requirement is very sensitive to these planning values. Set the variance planning value to the largest value within a plausible range for a conservatively large sample size.

Usage

size.ci.ratio.mean.ps(alpha, var, m1, m2, cor, r)

Arguments

alpha

alpha level for 1-alpha confidence

var

planning value of average variance of the two measurements

m1

planning value of mean for measurement 1

m2

planning value of mean for measurement 2

cor

planning value for correlation between measurements

r

desired upper to lower confidence interval endpoint ratio

Value

Returns the required sample size

Examples

size.ci.ratio.mean.ps(.05, 400, 150, 100, .7, 1.2)

# Should return:
# Sample size
#          21