compute_sample_size {ssev}

Compute sample size

Description

Function to compute the optimal sample size for a comparison of two means (with equal or unequal variances) or proportions. Function returns the standard sample size for an RCT with the specified power, as well as the optimal sample size for a population of size N.

Usage

compute_sample_size(means = NULL, sds = NULL, proportions = NULL,
  N = Inf, power = 0.8, sig.level = 0.05, ties = 0.5,
  .verbose = FALSE, ...)

Arguments

means

A vector of length 2 containing the (assumed) means of the two groups

sds

A vector containing the (assumed) standard deviations of the two groups. When only one element is supplied equal variances are assumed.

proportions

A vector of length 2 containing the (assumed) proportions of the two groups

N

Estimated population size

power

Desired power for the classical RCT

sig.level

Significance level of the test used (alpha)

ties

Probability of choosing the first group in case of a tie (i.e., H0 is not rejected)

.verbose

Whether or not verbose output should be provided, default FALSE

...

further arguments passed to or from other methods.

Value

An object of type ssev

Examples

compute_sample_size(means=c(0,1), sds=2, N=100)
compute_sample_size(means=c(0,1), sds=2, N=10000, power=.9)
compute_sample_size(means=c(0,1), sds=c(1,2), N=10000)
compute_sample_size(proportions=c(.5,.7), N=5000)