sim_power_equivalence_normal: Empirical Power for Equivalence (Normal Outcomes)

In ssutil: Sample Size Calculation Tools

Empirical Power for Equivalence (Normal Outcomes)

Description

Estimates the empirical power to detect equivalence among multiple groups assuming no true difference in normally distributed outcomes. Pairwise two-sample t-tests are used, and equivalence is declared if all confidence intervals for differences between group means lie entirely within the interval defined by llimit and ulimit.

Usage

sim_power_equivalence_normal(
  ngroups,
  npergroup,
  sd,
  llimit,
  ulimit,
  nsim,
  t_level = 0.95,
  conf.level = 0.95
)

Arguments

ngroups	Integer. Number of groups to compare
npergroup	Integer. Number of observations per group.
sd	Numeric. Standard deviation of the outcome distribution (common across groups).
llimit	Numeric. Lower equivalence limit.
ulimit	Numeric. Upper equivalence limit.
nsim	Integer. Number of simulations to perform.
t_level	Numeric. Confidence level used for the t-tests (e.g., 0.95 for 95% CI). Equivalence is assessed via a two-sided t_level CI, which is equivalent to two one-sided tests (TOST) each at a one-sided alpha of (1 - t_level) / 2. The default t_level = 0.95 therefore implements TOST at a one-sided alpha of 0.025; for the more common bioequivalence convention of one-sided alpha = 0.05 (e.g. FDA/EMA guidance), use t_level = 0.90 instead.
conf.level	Numeric. Confidence level for the empirical power estimate

Details

This function simulates data under the null hypothesis of no difference between groups and calculates the proportion of simulations in which all pairwise comparisons fall within the specified equivalence limits.

Value

An S3 object of class empirical_power_result, which contains the estimated empirical power and its confidence interval. The object can be printed, formatted, or further processed using associated S3 methods. See also empirical_power_result.

See Also

empirical_power_result

Examples

#Equivalence testing for three groups with log-scale outcome
sim_power_equivalence_normal(
  ngroups = 3,
  npergroup = 172,
  sd = 0.403,
  llimit = log10(2/3),
  ulimit = log10(3/2),
  nsim = 1000,
  t_level = 0.95
)

ssutil documentation built on Sept. 18, 2026, 1:06 a.m.