eventsNeeded2 {agpower}R Documentation

Number events needed (fixed sample size)

Description

Function to compute number events (L) needed to achieve given power with fixed sample size N.

Usage

eventsNeeded2(N, bta1, thta, alp = 0.05, pow = 0.8, ar = 0.5, Lmessage = FALSE)

Arguments

N

Sample size.

bta1

log-transform of rate ratio.

thta

Variance of frailty parameter.

alp

Two-sided alpha-level.

pow

Target power.

ar

Allocation ratio (Number control / Total).

Lmessage

If TRUE indicates how many estimates of L were negative before setting to Inf. Default FALSE.

Details

Assumes rate ratio < 1 is favourable to treatment. A negative estimated number of events indicates no number of events is sufficient under the input assumptions.

Value

The number of events (L) needed to achieve target power at one-sided Type I control level alpha/2, given the input assumptions.

Examples


eventsNeeded2(N = 500, bta1 = log(0.8), thta = 2, alp = 0.05, pow = 0.8)
eventsNeeded2(N = 500, bta1 = log(0.8), thta = 3, alp = 0.05, pow = 0.8)

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

  assumptions = tibble(alp = 0.05) %>%
  crossing(
    RR = c(0.6, 0.7, 0.8),
    thta = c(2, 3, 4),
    pow = 0.8,
    N = c(500, 1000)
  ) %>%
    mutate(L = eventsNeeded2(N = N, bta1 = log(RR), thta = thta, alp, pow))

  assumptions %>% data.frame()

}


[Package agpower version 0.1.2 Index]