signtest: Power calculation for sign test

In powertools: Power and Sample Size Tools

Power calculation for sign test

Description

The sign test is a nonparametric one-sample test of location, specifically, a test of whether the median equals (or is less than or greater than) zero. Its typical use is in place of a one-sample or paired t test when the normality assumption is violated. This function performs power and sample size calculations for a sign test using the normal approximation to the binomial distribution, based on Noether (1987) Sample size determination for some common nonparametric tests. JASA 82(398):645-647.

Power calculation for an exact sign test using the exact binomial test can be performed using the power_binom_test function from the MESS package; see Crespi CM (2025) Power and Sample Size in R. Routledge, New York, NY.

Usage

signtest(N = NULL, p = NULL, alpha = 0.05, power = NULL, sides = 2, v = FALSE)

Arguments

N	The sample size.
p	The probability of a positive difference when the alternative hypothesis is true.
alpha	The significance level (type 1 error rate); defaults to 0.05.
power	The specified level of power.
sides	Either 1 or 2 (default) to specify a one- or two-sided hypothesis test.
v	Either TRUE for verbose output or FALSE (default) to output computed argument only.

Details

When solving for p, two values, p and 1 - p, are returned. For a two-sided test, due to symmetry, the power for p is equal to the power for 1 - p. For a one-sided upper-tailed test (rejecting null hypothesis when median > 0), select the higher value. For a one-sided lower-tailed test (rejecting null hypothesis when median < 0), select the lower value.

Value

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

Examples

signtest(N = 40, p = 0.7, power = NULL, alpha = 0.05, sides = 1)

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