nNeeded2 {agpower}R Documentation

Function to compute sample size needed to achieve target power

Description

Computes sample size needed to achieve target power at one-sided Type I control level alp/2. A negative estimated sample size indicates no sample size is sufficient under the input assumptions.

Usage

nNeeded2(bta1, thta, L, alp = 0.05, pow = 0.8, ar = 0.5)

Arguments

bta1

log-transform of rate ratio.

thta

Variance of frailty parameter.

L

Number of events

alp

Two-sided alpha-level.

pow

Target power.

ar

Allocation ratio (Number control / Total)

Value

The sample size required given the input assumptions to achieve target power.

Examples


nNeeded2(bta1 = log(0.8), thta = 1, L = 1000, alp = 0.05, pow = 0.8)

if (require("dplyr") & require("tidyr")) {

  assumptions = tibble(alp = 0.05) %>%
  crossing(
    L = c(500, 1000, 1500),
    RR = c(0.6, 0.7, 0.8),
    thta = c(2, 3, 4),
    pow = 0.8
  ) %>%
    mutate(N = nNeeded2(bta1 = log(RR), thta = thta, L = L, alp = alp, pow = pow))

  assumptions %>% data.frame()

}


[Package agpower version 0.1.2 Index]