ObrienFleming {PwrGSD}

The O'Brien-Fleming Alpha Spending Function

Description

Stipulates alpha spending according to the O'Brien-Fleming spending function in the Lan-Demets boundary construction method. Its intended purpose is in constructing calls to GrpSeqBnds and PwrGSD.

Usage

ObrienFleming()

Value

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

type

Gives the spending function type, which is the character string "ObrienFleming"

call

returns the call

Note

The print method returns the call by default

Author(s)

Grant Izmirlian

References

see references under PwrGSD

See Also

LanDemets, Pow, Pocock, GrpSeqBnds, PwrGSD

Examples

## example 1: what is the result of calling a spending function
    ## A call to 'ObrienFleming' just returns the call
    ObrienFleming()

    ## but really its value is a list with a component named
    ## 'type' equal to "ObrienFleming" and a component named
    ## 'call' equal to the call.
    names(ObrienFleming)

    ObrienFleming()$type

    ObrienFleming()$call

## example 2: ...But the intended purpose of the spending functions 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)
    drift <- c(0.3836636,0.5117394,0.6918584,0.8657705,1.091984,
               1.311094,1.538582,1.818346,2.081775,2.345386)

    test <- GrpSeqBnds(frac=frac, EfficacyBoundary=LanDemets(alpha=0.05, spending=ObrienFleming),
                       FutilityBoundary=LanDemets(alpha=0.10, spending=Pocock),
                       drift=drift)