proportions.twoprops: Power Analysis for Testing Difference Between Two Proportions...

In pwrss: Statistical Power and Sample Size Calculation Tools

Power Analysis for Testing Difference Between Two Proportions (Normal Approximation and Exact Methods)

Description

Calculates power or sample size (only one can be NULL at a time) for two proportions using normal approximation method.

Validated via G*Power and PASS documentation.

NOTE: The pwrss.z.2props() function is deprecated, but it will remain available as a wrapper for the power.z.twoprops() function during the transition period.

Usage

power.z.twoprops(prob1, prob2, margin = 0,
                 n2 = NULL, n.ratio = 1,
                 power = NULL, alpha = 0.05,
                 alternative = c("two.sided", "one.sided", "two.one.sided"),
                 arcsine = FALSE, correct = FALSE,
                 paired = FALSE, rho.paired = 0.50,
                 std.error = c("pooled", "unpooled"),
                 ceiling = TRUE, verbose = TRUE, pretty = FALSE)

power.exact.twoprops(prob1, prob2, n2 = NULL, n.ratio = 1,
                     power = NULL, alpha = 0.05,
                     alternative = c("two.sided", "one.sided"),
                     paired = FALSE, rho.paired = 0.50,
                     method = c("exact", "approximate"),
                     ceiling = TRUE, verbose = TRUE, pretty = FALSE)

Arguments

prob1	probability of success in the first group.
prob2	probability of success in the second group.
margin	ignorable prob1 - prob2 difference. For two one-sided tests provide lower and upper margins in the form of c(lower, upper).
n2	integer; sample size for the second group.
n.ratio	sample size ratio (n1 / n2).
power	statistical power, defined as the probability of correctly rejecting a false null hypothesis, denoted as 1 - \beta.
alpha	type 1 error rate, defined as the probability of incorrectly rejecting a true null hypothesis, denoted as \alpha.
paired	logical; if TRUE samples are paired. FALSE by default.
rho.paired	correlation between paired observations.
method	character; whether to use "approximate" or "exact" method. Default is "exact" (only in the power.exact.twoprops() function).
arcsine	logical; whether arcsine transformation should be applied. Note that this only applies to independent proportions without continuity correction.
correct	logical; whether Yates' continuity correction should be applied to the test statistic. Ignored for the paired test.
std.error	character; whether to calculate standard error using "pooled" or "unpooled" standard deviation. Ignored for the paired test.
alternative	character; direction or type of the hypothesis test: "two.sided", "one.sided", or "two.one.sided".
ceiling	logical; TRUE rounds up sample size in each group.
verbose	logical; TRUE prints the output on the console.
pretty	logical; whether the output should show Unicode characters (if encoding allows for it). FALSE by default.

Value

parms	list of parameters used in calculation.
test	type of the test, which is "z" or "exact".
power	statistical power (1-\beta).
mean	mean of the alternative distribution.
sd	standard deviation of the alternative distribution.
null.mean	mean of the null distribution.
null.sd	standard deviation of the null distribution.
z.alpha	critical value(s).
n	sample size in the form of c(n1, n2) (applies to independent proportions).
n.total	total sample size (applies to independent proportions).
n.paired	paired sample size (applies to paired proportions).

References

Bulus, M., & Polat, C. (2023). pwrss R paketi ile istatistiksel guc analizi [Statistical power analysis with pwrss R package]. Ahi Evran Universitesi Kirsehir Egitim Fakultesi Dergisi, 24(3), 2207-2328. \Sexpr[results=rd]{tools:::Rd_expr_doi("10.29299/kefad.1209913")}

Examples

  # power
  power.z.twoprops(prob1 = 0.65, prob2 = 0.60,
                   alpha = 0.05, n2 = 500,
                   alternative = "one.sided")

  # sample size
  power.z.twoprops(prob1 = 0.65, prob2 = 0.60,
                   alpha = 0.05, power = 0.80,
                   alternative = "one.sided")

pwrss documentation built on Sept. 16, 2025, 9:11 a.m.