Pointwise Spending Function

The function sfPoints implements a spending function with values specified for an arbitrary set of specified points. It is now recommended to use sfLinear rather than sfPoints. If using sfPoints() in a design, it is recommended to specify how to interpolate between the specified points (e.g,, linear interpolation); also consider fitting smooth spending functions; see vignette("SpendingFunctionOverview").

Usage

sfPoints(alpha, t, param)

Arguments

alpha: Real value \(> 0\) and no more than 1. Normally, alpha=0.025 for one-sided Type I error specification or alpha=0.1 for Type II error specification. However, this could be set to 1 if for descriptive purposes you wish to see the proportion of spending as a function of the proportion of sample size/information.
t: A vector of points with increasing values from >0 and <=1. Values of the proportion of sample size/information for which the spending function will be computed.
param: A vector of the same length as t specifying the cumulative proportion of spending to corresponding to each point in t; must be >=0 and <=1.

Value

An object of type spendfn. See vignette("SpendingFunctionOverview") for further details.

Note

The gsDesign technical manual is available at https://keaven.github.io/gsd-tech-manual/.

References

Jennison C and Turnbull BW (2000), Group Sequential Methods with Applications to Clinical Trials. Boca Raton: Chapman and Hall.

Author

Keaven Anderson keaven_anderson@merck.com