sampleSize_count: Estimate sample size for count-rate equivalence

In SimTOST: Sample Size Estimation for Bio-Equivalence Trials Through Simulation

Estimate sample size for count-rate equivalence

Description

Searches for the smallest number of subjects per arm whose simulated power reaches the target for a rate-ratio equivalence test.

Usage

sampleSize_count(
  power = 0.8,
  rate_test,
  rate_reference,
  exposure = 1,
  margin_lower = 0.8,
  margin_upper = 1.25,
  model = c("poisson", "negative-binomial"),
  dispersion = 0.1,
  alpha = 0.05,
  nsim = 5000,
  seed = NULL,
  lower = 2,
  upper = 500,
  design = c("parallel", "2x2"),
  k = NULL,
  endpoint_corr = NULL,
  type_y = NULL,
  adjust = c("none", "bonferroni", "sidak", "t", "pc", "partial-conjunction",
    "partial_conjunction", "sequential"),
  sigmaB = 0,
  Eper = c(0, 0),
  Eco = c(0, 0),
  dropout = c(0, 0),
  optimization_method = c("fast", "step-by-step"),
  step.power = 6,
  step.up = TRUE,
  pos.side = FALSE,
  maxiter = 1000,
  ncores = 1,
  .warn_redundant_bon = TRUE
)

Arguments

power	Target power.
rate_test	Event rate in the test arm.
rate_reference	Event rate in the reference arm.
exposure	Exposure per subject; a scalar or one value per endpoint.
margin_lower	Lower rate-ratio equivalence margin.
margin_upper	Upper rate-ratio equivalence margin.
model	Count model: "poisson" or "negative-binomial".
dispersion	Positive negative-binomial dispersion parameter. The per-subject negative-binomial size is 1 / dispersion; parallel-arm totals use size n / dispersion.
alpha	One-sided significance level.
nsim	Number of simulated trials.
seed	Optional random seed.
lower	Minimum subjects per arm.
upper	Maximum subjects per arm.
design	Trial design: "parallel" or "2x2". In a crossover design, the returned sample size is per sequence.
k	Number of endpoints that must demonstrate equivalence. Defaults to all supplied endpoints.
endpoint_corr	Endpoint correlation matrix used by the Gaussian copula for multi-endpoint count simulations. The default is independence.
type_y	Numeric endpoint hierarchy used with adjust = "seq": 1 for primary/co-primary endpoints and 2 for secondary endpoints.
adjust	Multiplicity adjustment for endpoint-wise one-sided alpha: "none", "bonferroni", "sidak", "t", or "seq"/"sequential". The "t" option uses Mielke's strong k-out-of-m calibration alpha / (m - k + 1); legacy partial-conjunction labels are accepted.
sigmaB	Between-subject standard deviation for the count 2x2 design.
Eper	Period effects for the count 2x2 design.
Eco	Carry-over effects for the count 2x2 design.
dropout	Dropout proportions for the count 2x2 design.
optimization_method	Search method. "fast" brackets the power crossing and uses integer bisection; "step-by-step" evaluates every candidate sample size.
step.power	Initial power-of-two jump used by the fast search.
step.up	Direction of the initial bracketing search.
pos.side	Retained for compatibility with sampleSize(); count searches return the smallest candidate reaching the target.
maxiter	Maximum number of power evaluations.
ncores	Number of worker processes used for count simulations. Set to 1 for serial execution. Parallel execution splits nsim into reproducible independent chunks and combines the resulting successes.
.warn_redundant_bon	Logical. If TRUE, warn about redundant or uncalibrated multiplicity configurations.

Value

An object of class countss containing the selected sample size, achieved power, confidence interval, input parameters, and the search history in table.iter and table.test. For count outcomes, table.iter has one row per evaluated candidate sample size. table.test contains complete-trial, comparator, and endpoint decision indicators for each simulated trial and candidate. The count kernel returns aggregate decision counts rather than raw endpoint-level test statistics, so component columns preserve the simulated marginal success counts.

Examples

SimTOST:::sampleSize_count(0.80, 0.20, 0.20, lower = 100, upper = 2000,
                 nsim = 100, seed = 1)

SimTOST documentation built on Oct. 9, 2026, 5:07 p.m.