size.ci.ratio.mean2: Sample size for a 2-group mean ratio confidence interval

In statpsych: Statistical Methods for Psychologists

Sample size for a 2-group mean ratio confidence interval

Description

Computes the sample size in each group required to estimate a ratio of population means with desired confidence interval precision in a 2-group design. 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.mean2(alpha, var, m1, m2, r, R)

Arguments

alpha	alpha level for 1-alpha confidence
var	planning value of average within-group variance
m1	planning value of mean for group 1
m2	planning value of mean for group 2
r	desired upper to lower confidence interval endpoint ratio
R	n2/n1 ratio

Value

Returns the required sample size for each group

Examples

size.ci.ratio.mean2(.05, .4, 3.5, 3.1, 1.2, 2)

# Should return:
# n1   n2
# 53  106
 

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