The Haybittle method of Boundary Construction
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
1 
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

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
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28  ## 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))
