GroupSeq (version 1.0)

alphaByUseFunction: Computes alpha by a use function

Description

This function computes type I error to spend at each analysis using an alpha-spending function.

Usage

alphaByUseFunction(whatSpendingFunctionIsUsed, n, alpha, phi, OneOrTwoSidedBounds, t)

Arguments

whatSpendingFunctionIsUsed

indicates type I error spending rate function and is an integer value.

n

is the number of interim analyses so far

alpha

is the desired overall size

phi

optional Parameter referring to Power Family

OneOrTwoSidedBounds

One-(OneOrTwoSidedBounds==1) or Two-sided bounds(OneOrTwoSidedBounds==2)

t

is the vector of information times

Value

• probExit
  the vector of type I error (e.g. exit probabilities) spent at each analysis.

Details

The use function, or type I error spending rate, corresponds to the Alpha 1 star, Alpha 2 star and Alpha 3 star in Lan & DeMets(1983).

References

Lan & DeMets 1983 Biometrika http://www.biostat.wisc.edu/landemets/

See Also

groupseq, asHSdeCani, asPowerFamily asOBF, asPocock

Examples

## One-sided using O'Brien-Fleming Type
alphaByUseFunction(1,3,0.05,0,1,c(0.33,0.66,1.0))

## Two-sided using Power family: $\alpha t^{\phi}$ with $\phi$==1
alphaByUseFunction(3,3,0.05,1,2,c(0.33,0.66,1.0))