Ch7-Haybittle: The Haybittle method of Boundary Construction

In PwrGSD: Power in a Group Sequential Design

Description

The function Haybittle is used in calls to the functions GrpSeqBnds and PwrGSD as a possible setting for the argument EfficacyBoundary. NOTE: the Haybittle method is not used for construction a futility boundary (does this even make sense?). The Haybittle method is one of four currently availiable choices, the others being LanDemets, SC (stochastic curtailment), and user specified.

Usage

Haybittle(alpha, b.Haybittle, from = NULL, to = NULL)

Arguments

alpha	The total probability of type I error.
b.Haybittle	User specified efficacy boundary at all but the last analysis.
from	WARNING EXPERIMENTAL: See the documentation under LanDemets or SC. I'm not quite sure if this works or even makes sense. Don't use it, ok?
to	See above.

Details

The Haybittle method is the simplest of all methods for efficacy boundary construction. You just specify a value such as 3 which is so large that multiple testing with standard normal criterion 3 (upper quantile is 0.00135) means that after 20 analyses you've spent only 0.027. The value of the criterion for the final analysis is determined so that the total type I error is obtained.

Value

An object of class boundary.construction.method which is really a list with the following components. The print method displays the original call.

type	Gives the boundary construction method type, which is the character string "Haybittle"
alpha	The numeric value passed to the argument 'alpha' which is the total probability of type I error.
b.Haybittle	The numeric value passed to the argument 'b.Haybittle' which is the user specified efficacy boundary at all but the last analysis.
from	Description of 'comp2'
to	You're not using this, right?
call	see above.

Note

The print method returns the call by default

Author(s)

Grant Izmirlian

References

see references under PwrGSD

See Also

LanDemets, SC, GrpSeqBnds, and PwrGSD

Examples

## example 1: what is the result of calling a Boundary Construction Method function
    ## A call to 'Haybittle' just returns the call
    Haybittle(alpha=0.05, b.Haybittle=3)
    
    ## It does arguement checking...this results in an error
    ## Not run: 
      Haybittle(alpha=0.05)
    
## End(Not run)
    
    ## but really its value is a list with the a component containing
    ## the boundary method type, "LanDemts", and components for each
    ## of the arguments.
    names(Haybittle(alpha=0.05, b.Haybittle=3))

    Haybittle(alpha=0.05, b.Haybittle=3)$type
    Haybittle(alpha=0.05, b.Haybittle=3)$alpha
    Haybittle(alpha=0.05, b.Haybittle=3)$b.Haybittle
    Haybittle(alpha=0.05, b.Haybittle=3)$call

## example 2: ...But the intended purpose of the spending functions its
    ## intended purpose is in constructing calls to 'GrpSeqBnds' and to 'PwrGSD':
     

    frac <- c(0.07614902,0.1135391,0.168252,0.2336901,0.3186155,
              0.4164776,0.5352199,0.670739,0.8246061,1)

    test <- GrpSeqBnds(frac=frac, EfficacyBoundary=Haybittle(alpha=0.025, b.Haybittle=3))

PwrGSD documentation built on May 2, 2019, 4:54 p.m.