multisite.cont: Power for test of average treatment effect in a multisite...
In powertools: Power and Sample Size Tools

multisite.cont

R Documentation

Power for test of average treatment effect in a multisite trial

Description

Performs power and sample size calculations for a multisite trial with a continuous (normal) outcome variable. Can solve for power, J, m or alpha.

Usage

multisite.cont(
  m = NULL,
  m.sd = 0,
  alloc.ratio = 1,
  J = NULL,
  delta = NULL,
  sd = 1,
  icc0 = NULL,
  icc1 = NULL,
  Rsq = 0,
  alpha = 0.05,
  power = NULL,
  sides = 2,
  v = FALSE
)

Arguments

`m`	The mean cluster/site size (number of participants per site).
`m.sd`	The standard deviation of cluster/site sizes (provide if unequal number of participants per site); defaults to 0.
`alloc.ratio`	The allocation ratio of condition 2/condition 1 within site; defaults to 1.
`J`	The total number of sites.
`delta`	The difference between the condition 1 and condition 2 means under the alternative minus the difference under the null hypothesis.
`sd`	The total standard deviation of the outcome variable; defaults to 1.
`icc0`	The proportion of total variance of the outcome attributable to variation in site-level means.
`icc1`	The proportion of total variance of the outcome attributable to variation in the treatment effect across sites.
`Rsq`	The estimated R^2 for regressing the outcome on the covariates; defaults to 0.
`alpha`	The significance level (type 1 error rate); defaults to 0.05.
`power`	The specified level of power.
`sides`	Either 1 or 2 (default) to specify a one- or two- sided hypothesis test.
`v`	Either TRUE for verbose output or FALSE (default) to output computed argument only.

Details

In a multisite trial design, participants are randomized to conditions within site.

Value

A list of the arguments (including the computed one).

Examples

multisite.cont(m = 20, J = 10, delta = 3, sd = sqrt(40), icc0 = 0.1, icc1 = 0)
multisite.cont(m = 20, J = 10, delta = 3, sd = sqrt(48), icc0 = 0.095, icc1 = 0.048)
multisite.cont(m = 20, alloc.ratio = 1.5, J = 10, delta = 0.43, icc0 = 0.095, icc1 = 0.048)
multisite.cont(m = 10, J = NULL, delta = 0.5, sd = 1, icc0 = 0, icc1 = 0.05, power = 0.8)
multisite.cont(m = 20, m.sd = 5, J = 10, delta = 3, sd = sqrt(48), icc0 = 0.095, icc1 = 0.048)
multisite.cont(m = 20, J = 10, delta = 3, sd = sqrt(48), icc0 = 0.095,
icc1 = 0.048, Rsq = 0.5^2)

powertools documentation built on April 4, 2025, 5:02 a.m.