print.findn: Printing a findn Object

In findn: Simulation Based Sample Size Estimation

Printing a findn Object

Description

Displays details about a sample size estimation from a findn object.

Usage

## S3 method for class 'findn'
print(
  x,
  details = c("low", "high"),
  max_n = NULL,
  digits = 3,
  invisible = FALSE,
  ...
)

Arguments

x	Object of class findn.
details	Either "low" (default) or "high". See also 'Details'.
max_n	If details = "high" the predicted power values and confidence intervals are shown for all sample sizes from 1 to max_n if max_n is non-NULL. See also 'Details'.
digits	Number of decimal places to be shown.
invisible	Whether the results should be printed or only assigned.
...	Further arguments.

Details

When details = "low", only the point estimate (i.e., the smallest sample for which the predicted power exceeds the target power), the "minimum sufficient sample size" (i.e., the smallest sample size for which the lower limit of the level interval for the predicted power exceeds the target power) and an exit message. The exit message shows whether the chosen stopping rule was satisfied. If details = "high" then the default behaviour (i.e. when max_n = NULL) is to display all sample sizes, their predicted power values and the alpha whether their power exceeds the target power, and the three largest sample sizes that are smaller than the smallest sample size that is rated uncertain and the three smallest sample sizes which are greater than the smallest sample size that is rated uncertain. If details = "high" and max_n is non-NULL, then the sample sizes, their predicted power values and the confidence intervals for the predicted power values from 1 to max_n are displayed.

Value

findn returns an object of class findn which contains the following elements:

sample_size	the sample size estimate
fit	the model coefficients and covariance matrix from the last Bayesian probit regression model
all_evals	all evaluated sample sizes
targ	the target power
level	the significance level for the confidence intervals used for the stopping criteria
exit.mes	a message about wheter the stopping criterion was reached with the number of simulations given by max_evals

By default, a list containing the point estimate for the sample size, the minimum sufficient sample size (i.e. the smallest sample size for which the lower limit of the confidence interval for the estimated power is larger than the target power) and a message whether the stopping criterion was reached is printed.

Examples

# Function that simulates the outcomes of a two-sample t-test
ttest <- function(mu1 = 0, mu2 = 1, sd, n, k) {
  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))
}

# Create a findn object
res_ttest <- findn(fun = ttest, targ = 0.8, k = 25, start = 100, 
  init_evals = 100, r = 4, stop = "evals", max_evals = 2000, 
  level = 0.05, var_a = 0.05, var_b = 1, alpha = 0.025, 
  alternative = "one.sided", sd = 2, verbose = FALSE)

# print with default settings
print(res_ttest, details = "low", digits = 3)

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