propodds: Power calculations for ordinal categorical variable under...

In powertools: Power and Sample Size Tools

Power calculations for ordinal categorical variable under proportional odds assumption

Description

Performs power and sample size calculation for a comparison of two groups on an ordinal categorical response variable. Assumes that response probabilities follow the proportional odds assumption. Can solve for power, n1, n.ratio and alpha.

Usage

propodds(pC, OR, n1, n.ratio = 1, alpha = 0.05, power = NULL, v = FALSE)

Arguments

pC	Vector of response probabilities in control group (group 1). Must sum to 1. Categories are ordered from best to worst.
OR	Odds ratio when the alternative is true. Must be greater than 1.
n1	Sample size for group 1 (control group).
n.ratio	The ratio n2/n1 between the sample sizes of two groups; defaults to 1 (equal group sizes).
alpha	The significance level (type 1 error rate); defaults to 0.05.
power	The specified level of power; defaults to 0.8.
v	Either TRUE for verbose output or FALSE (default) to output computed argument only.

Details

Whitehead J. (1993) Sample size calculations for ordered categorical data. Statistics in Medicine, 12(24):2257–2271

Value

A list of the arguments (including the computed one).

Examples

library(Hmisc)
pC <- c(0.2, 0.5, 0.2, 0.1)
propodds(pC = pC, OR = 2.5, n1 = 65, n.ratio = 1, alpha = 0.05)

powertools documentation built on April 4, 2025, 5:02 a.m.