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Sample Size or Power for Two-Sample Proportion Test

Source: R/two_prop_size.R
two_prop_size.Rd

Calculates sample size or power for a two-sample proportion test.

Usage

two_prop_size(
  pA,
  pB,
  delta = NULL,
  kappa = 1,
  alpha,
  beta = NULL,
  nB = NULL,
  test_type = "2-side"
)

Arguments

pA

Numeric. True proportion of group A.

pB

Numeric. True proportion of group B.

delta

Numeric (optional). Margin for "non-inferiority" or "equivalence" test. Required for "non-inferiority" or "equivalence" test.

kappa

Numeric. Ratio of sample sizes (nA/nB). Default is 1.

alpha

Numeric. Type I error rate.

beta

Numeric (optional). Type II error rate. Required for sample size calculation.

nB

Integer (optional). Sample size for group B. Required for power calculation.

test_type

Character. "2-side", "1-side", "non-inferiority", or "equivalence". Default is "2-side".

Value

Numeric. Returns sample size (if beta is given), or power (if nB is given).

Note

Only one of beta (for sample size calculation) or nA/nB (for power calculation) should be specified.

Required arguments by test_type:

  • "2-side"/"1-side":

    • For sample size: pA, pB, alpha, beta

    • For power: pA, pB, alpha, nB

  • "non-inferiority"/"equivalence":

    • For sample size: pA, pB, delta, alpha, beta

    • For power: pA, pB, delta, alpha, nB

Examples

# Sample size for `"2-side"` test
two_prop_size(pA = 0.65, pB = 0.85, kappa = 1,
              alpha = 0.05, beta = 0.2, test_type = "2-side")
#> [1] 70

# Power of `"2-side"` test
two_prop_size(pA = 0.65, pB = 0.85, kappa = 1,
              alpha = 0.05, nB = 70, test_type = "2-side")
#> [1] 0.8019139

# Sample size for `"1-side"` test
two_prop_size(pA = 0.65, pB = 0.85, kappa = 1,
              alpha = 0.05, beta = 0.2, test_type = "1-side")
#> [1] 55

# Power of `"1-sided"` test
two_prop_size(pA = 0.65, pB = 0.85, kappa = 1,
              alpha = 0.05, nB = 55, test_type = "1-side")
#> [1] 0.8008219

# Sample size for `"non-inferiority"` test
two_prop_size(pA = 0.85, pB = 0.65, delta = -0.1, kappa = 1,
              alpha = 0.05, beta = 0.2, test_type = "non-inferiority")
#> [1] 25

# Power of `"non-inferiority"` test
two_prop_size(pA = 0.85, pB = 0.65, delta = -0.1, kappa = 1,
              alpha = 0.05, nB = 25, test_type = "non-inferiority")
#> [1] 0.8085998

# Sample size for `"equivalence"` test
two_prop_size(pA = 0.65, pB = 0.85, delta = 0.05, kappa = 1,
              alpha = 0.05, beta = 0.2, test_type = "equivalence")
#> [1] 136

# Power of `"equivalence"` test
two_prop_size(pA = 0.65, pB = 0.85, delta = 0.05, kappa = 1,
              alpha = 0.05, nB = 136, test_type = "equivalence")
#> [1] 0.8033294