| % File src/library/stats/man/power.anova.test.Rd |
| % Part of the R package, https://www.R-project.org |
| % Copyright 1995-2007 R Core Team |
| % Distributed under GPL 2 or later |
| |
| \name{power.anova.test} |
| \alias{power.anova.test} |
| \encoding{UTF-8} |
| \title{Power Calculations for Balanced One-Way Analysis of Variance Tests} |
| \usage{ |
| power.anova.test(groups = NULL, n = NULL, |
| between.var = NULL, within.var = NULL, |
| sig.level = 0.05, power = NULL) |
| } |
| \arguments{ |
| \item{groups}{Number of groups} |
| \item{n}{Number of observations (per group)} |
| \item{between.var}{Between group variance} |
| \item{within.var}{Within group variance} |
| \item{sig.level}{Significance level (Type I error probability)} |
| \item{power}{Power of test (1 minus Type II error probability)} |
| } |
| \description{ |
| Compute power of test or determine parameters to obtain target power. |
| } |
| |
| \details{ |
| Exactly one of the parameters \code{groups}, \code{n}, \code{between.var}, |
| \code{power}, \code{within.var}, and \code{sig.level} must be passed as NULL, |
| and that parameter is determined from the others. Notice that |
| \code{sig.level} has non-NULL default so NULL must be explicitly |
| passed if you want it computed. |
| } |
| \value{ |
| Object of class \code{"power.htest"}, a list of the arguments |
| (including the computed one) augmented with \code{method} and |
| \code{note} elements. |
| } |
| |
| \author{Claus \enc{Ekstrøm}{Ekstroem}} |
| \note{ |
| \code{uniroot} is used to solve power equation for unknowns, so |
| you may see errors from it, notably about inability to bracket the |
| root when invalid arguments are given. |
| } |
| \seealso{\code{\link{anova}}, \code{\link{lm}}, \code{\link{uniroot}}} |
| |
| \examples{ |
| power.anova.test(groups = 4, n = 5, between.var = 1, within.var = 3) |
| # Power = 0.3535594 |
| |
| power.anova.test(groups = 4, between.var = 1, within.var = 3, |
| power = .80) |
| # n = 11.92613 |
| |
| ## Assume we have prior knowledge of the group means: |
| groupmeans <- c(120, 130, 140, 150) |
| power.anova.test(groups = length(groupmeans), |
| between.var = var(groupmeans), |
| within.var = 500, power = .90) # n = 15.18834 |
| } |
| \keyword{htest} |