powertools (version 1.0.0)

anova2way.c.bal: Power calculation for two-way balanced analysis of variance contrast test

Description

Performs sample size and power calculations for a test of a contrast between levels of a factor in a two-way ANOVA with balanced data (that is, equal sized cells). Can be used to solve for power, n (sample size per cell), or alpha. For unbalanced data, see anova2way.c.unbal. For a test of a contrast among cell means, see anova2way.se.bal.

Usage

anova2way.c.bal(
  n = NULL,
  mmatrix = NULL,
  cvec = NULL,
  factor = c("a", "b"),
  sd = 1,
  Rsq = 0,
  ncov = 0,
  alpha = 0.05,
  power = NULL,
  v = FALSE
)

Value

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

Arguments

n

The sample size per cell

mmatrix

A matrix of cell means (see example).

cvec

A vector of contrast coefficients c(c1, c2, ...).

factor

Either "a" for rows or "b" for columns depending on which factor the contrast test is being made on.

sd

The estimated standard deviation within each cell; defaults to 1.

Rsq

The estimated R^2 for regressing the outcome on the covariates; defaults to 0.

ncov

The number of covariates adjusted for in the model; defaults to 0.

alpha

The significance level (type 1 error rate); defaults to 0.05.

power

The specified level of power.

v

Either TRUE for verbose output or FALSE (default) to output computed argument only.

Examples

mmatrix <- matrix(c(9.3, 8.9, 8.5, 8.7, 8.3, 7.3), nrow = 2, byrow = TRUE)
anova2way.c.bal(n = 30, mmatrix = mmatrix, cvec = c(1, 0, -1), factor = "b",
sd = 2, alpha = 0.05)