powerbf01: Power and sample size calculations for z-test Bayes factor

In bfpwr: Power and Sample Size Calculations for Bayes Factor Analysis

Power and sample size calculations for z-test Bayes factor

Description

Compute probability that z-test Bayes factor is smaller than a specified threshold (the power), or determine sample size to obtain a target power.

Usage

powerbf01(
  n = NULL,
  power = NULL,
  k = 1/10,
  sd = 1,
  null = 0,
  pm,
  psd,
  type = c("two.sample", "one.sample", "paired"),
  dpm = pm,
  dpsd = psd,
  nrange = c(1, 10^5)
)

Arguments

n	Sample size (per group for two-sample tests). Has to be NULL if power is specified. Defaults to NULL
power	Target power. Has to be NULL if n is specified. Defaults to NULL
k	Bayes factor threshold. Defaults to 1/10, Jeffreys' threshold for 'strong evidence' against the null hypothesis
sd	Standard deviation of one observation (for type = "two.sample" or type = "one.sample") or of one difference within a pair of observations (type = "paired"). Is assumed to be known. Defaults to 1
null	Mean difference under the point null hypothesis. Defaults to 0
pm	Mean of the normal prior assigned to the mean difference under the alternative in the analysis
psd	Standard deviation of the normal prior assigned to the mean difference under the alternative in the analysis. Set to 0 to obtain a point prior at the prior mean
type	The type of test. One of "two.sample", "one.sample", "paired". Defaults to "two.sample"
dpm	Mean of the normal design prior assigned to the mean difference. Defaults to the same value as the analysis prior pm
dpsd	Standard deviation of the normal design prior assigned to the mean difference. Defaults to the same value as the analysis prior psd
nrange	Sample size search range over which numerical search is performed (only taken into account when n is NULL). Defaults to c(1, 10^5)

Details

This function provides a similar interface as stats::power.t.test. It also assumes that the data are continuous and that the parameter of interest is either a mean or a (standardized) mean difference. For some users, the low-level functions nbf01 (to directly compute the sample size for a fixed power) and pbf01 (to directly compute the power for a fixed sample size) may also be useful because they can be used for other data and parameter types.

Value

Object of class "power.bftest", a list of the arguments (including the computed one) augmented with method and note elements

Note

A warning message will be displayed in case that the specified target power is not achievable under the specified analysis and design priors.

Author(s)

Samuel Pawel

See Also

plot.power.bftest, nbf01, pbf01, bf01

Examples

## determine power
powerbf01(n = 100, pm = 0, psd = 1, dpm = 0.5, dpsd = 0)

## determine sample size
powerbf01(power = 0.99, pm = 0, psd = 1, dpm = 0.5, dpsd = 0)

bfpwr documentation built on June 8, 2025, 1:40 p.m.