The Haybittle method of Boundary Construction
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 implemented as a futility boundary method The Haybittle method
is one of four currently availiable choices (efficacy only), the others being
LanDemets
, SC
(stochastic curtailment), and user specified.
Haybittle(alpha, b.Haybittle, from = NULL, to = NULL)
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
|
to |
See above. |
The Haybittle approach is conceptually the simplest of all methods for efficacy boundary
construction. However, as it spends nearly no alpha until the end, is for all practical
purposes equivalent to a single analysis design and to be considered overly
conservative. This method sets all the boundary points equal to b.Haybittle
, a
user specified value (try 3) for all analyses except the last, which is calculated so as
to result in the total type I error, set with the argument alpha
.
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. |
The print method returns the call by default
Grant Izmirlian
see references under PwrGSD
LanDemets
, SC
, GrpSeqBnds
, and
PwrGSD
## 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 ## 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))
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