multisite.cont {powertools} | 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)