R/sample.size.mean.z.onesample.R

In burrm/lolcat: Miscellaneous Useful Functions

sample.size.mean.z.onesample <- function(
  effect.size
  ,variance
  ,alpha = .05
  ,beta = .1
  ,alternative = c("two.sided","less","greater")
  ,details = TRUE
  ,power.from.actual = F #report parameter power instead of true power
) {
  validate.htest.alternative(alternative = alternative)
  se.est <- sqrt(variance)
  
  z_alpha <- qnorm(ifelse(alternative[1] == "two.sided",alpha/2,alpha), lower.tail = F)
  z_beta  <- qnorm(beta, lower.tail = F)
  
  n <- ((z_alpha + z_beta) * se.est / effect.size)^2 
  
  if (alternative[1] == "greater" && effect.size < 0) {
    n <- NA
  }
  
  if (alternative[1] == "less" && effect.size > 0) {
    n <- NA
  }
  
  n.rounded <- ceiling(n)
  
  if (power.from.actual) {
    
    power <- 1-beta
    
  } else {
  
    #beta <- pnorm(sqrt(n.rounded) * effect.size/se.est  - qnorm(ifelse(alternative[1] == "two.sided",alpha/2,alpha), lower.tail = F)
    #           , lower.tail = F)
    
    power <- power.mean.z.onesample(sample.size = n.rounded, 
                           effect.size = effect.size,
                           variance = variance,
                           alpha=alpha,
                           alternative = alternative,
                           details=FALSE
                           )
    
    beta <- 1-power
    
  }
  
  if (details) {
  as.data.frame(list(test="z"
                     ,type = "one.sample"
                     ,alternative = alternative[1]
                     ,sample.size = n.rounded
                     ,actual = n
                     ,effect.size = effect.size
                     ,variance = variance
                     ,alpha = alpha
                     ,conf.level = 1-alpha
                     ,beta = beta
                     ,power = power
                     ))
  
  }
  else {
    n.rounded
  }
}