pwrss (version 1.3.1)

power.exact.twoprops: Power Analysis for Testing the Difference Between Two Proportions (Exact Method)

Description

Calculates power or sample size (only one can be NULL at a time) for two proportions using the exact method. The function is a wrapper for power.exact.mcnemar (if paired == TRUE), or power.exact.fisher (if paired == FALSE)

Validated via G*Power and PASS documentation.

Usage

power.exact.twoprops(
  prob1 = NULL,
  prob2 = NULL,
  req.sign = "+",
  n.ratio = 1,
  n2 = NULL,
  power = NULL,
  alpha = 0.05,
  alternative = c("two.sided", "one.sided"),
  paired = FALSE,
  rho.paired = 0.5,
  method = c("exact", "approximate"),
  ceil.n = TRUE,
  verbose = 1,
  utf = FALSE
)
power.exact.twoprop(
  prob1 = NULL,
  prob2 = NULL,
  req.sign = "+",
  n.ratio = 1,
  n2 = NULL,
  power = NULL,
  alpha = 0.05,
  alternative = c("two.sided", "one.sided"),
  paired = FALSE,
  rho.paired = 0.5,
  method = c("exact", "approximate"),
  ceil.n = TRUE,
  verbose = 1,
  utf = FALSE
)

Value

parms

list of parameters used in calculation.

test

type of the test, which is "z" or "exact".

delta

difference between prob1 and prob2

odds.ratio

Odds-ratio \((prob1 / (1 - prob1)) / (prob2 / (1 - prob2))\)

size

... (applies to paired proportions).

prob

... (applies to paired proportions).

null.prob

... (applies to paired proportions).

binom.alpha

critical value(s) (applies to paired proportions).

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.

alternative

standard deviation of the null distribution.

z.alpha

critical value(s).

power

statistical power \((1 - \beta)\).

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).

Arguments

prob1

probability of success in the first group.

prob2

probability of success in the second group.

req.sign

whether estimated prob is smaller or larger than the other (when minimum detectable prob is of interest).

n.ratio

sample size ratio (n1 / n2).

n2

integer; sample size for the second group.

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 \(\alpha\).

alternative

character; the direction or type of the hypothesis test: "two.sided" or "one.sided".

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).

ceil.n

logical; TRUE rounds up sample size in each group.

verbose

1 by default (returns test, hypotheses, and results), if 2 a more detailed output is given (plus key parameters and definitions), if 0 no output is printed on the console.

utf

logical; whether the output should show Unicode characters (if encoding allows for it). FALSE by default.

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. https://doi.org/10.29299/kefad.1209913

Examples

  # power
  power.exact.twoprops(prob1 = 0.70, prob2 = 0.60,
                       alpha = 0.05, n2 = 500,
                       alternative = "one.sided")

  power.exact.twoprops(prob1 = 0.70, prob2 = 0.60,
                       alpha = 0.05, n2 = 500,
                       alternative = "one.sided",
                       paired = TRUE)

  # sample size
  power.exact.twoprops(prob1 = 0.70, prob2 = 0.60,
                       alpha = 0.05, power = 0.80,
                       alternative = "one.sided")

  power.exact.twoprops(prob1 = 0.70, prob2 = 0.60,
                       alpha = 0.05, power = 0.80,
                       alternative = "one.sided",
                       paired = TRUE)