findn_maruo: Find the Sample Size Using the Algorithm by Maruo et al.

In findn: Simulation Based Sample Size Estimation

Find the Sample Size Using the Algorithm by Maruo et al.

Description

findn_maruo estimates the sample size for a certain target function based on repeated simulations using a model based approach proposed by Maruo et al. (2018).

Usage

findn_maruo(fun, targ, start = 10, k = 100, ...)

Arguments

fun	A function that estimates the power of a trial. The function has to take at least two arguments: n, the sample size and k, the number of iterations.
targ	The target power. Must be either 0.8 or 0.9.
start	Starting value for the algorithm. Maruo et al. suggest to use 10.
k	Number of trial simulations to use in fun to estimate the power.
...	Further optional arguments.

Value

findn_maruo returns a list containing the point estimate for the sample size and a list of all sample sizes that for which the trial function was evaluated.

References

Maruo, K., Tada, K., Ishil, R. and Gosho M. (2018) An Efficient Procedure for Calculating Sample Size Through Statistical Simulations, Statistics in Biopharmaceutical Research 10, 1-8.

Examples

# Function that simulates the outcomes of a two-sample t-test
ttest <- function(n, k, mu1 = 0, mu2 = 1, sd = 2) {
  sample1 <- matrix(rnorm(n = ceiling(n) * k, mean = mu1, sd = sd),
    ncol = k)
  mean1 <- apply(sample1, 2, mean)
  sd1_hat <- apply(sample1, 2, sd)
  sample2 <- matrix(rnorm(n = ceiling(n) * k, mean = mu2, sd = sd),
    ncol = k)
  mean2 <- apply(sample2, 2, mean)
  sd2_hat <- apply(sample2, 2, sd)
  sd_hat <- sqrt((sd1_hat^2 + sd2_hat^2) / 2)
  teststatistic <- (mean1 - mean2) / (sd_hat * sqrt(2 / n))
  crit <- qt(1 - 0.025, 2 * n - 2)
  return(mean(teststatistic < -crit))
}

findn_maruo(fun = ttest, targ = 0.8)

findn documentation built on March 30, 2026, 9:07 a.m.