acondpow: Compute Approximate Conditional Power
In raredd/desmon: Functions for design and monitoring of clinical trials

acondpow

R Documentation

Compute Approximate Conditional Power

Description

Computes an approximation to the conditional power of a sequential test based on the asymptotic normality of the statistic.

Usage

acondpow(za, power, zs, infr)

Arguments

`za`	standard normal critical value at final analysis
`power`	the overall planned power of the sequential test
`zs`	value of the test statistic on the standard normal scale at the current interim analysis
`infr`	information fraction (proportion of total information) at the current interim analysis

Details

Computes an approximation to the conditional probability of the test being rejected at the final analysis (i.e., that the test statistic will be > za), conditional on the current data, if the alternative for which the sequential test has power power is true. The approximation is based on asymptotic joint normality of the test statistic at the current and final analysis, and on the increment in the information being independent of the current data.