# commonbounds: Commonly Used Group Sequential Boundaries In ldbounds: Lan-DeMets Method for Group Sequential Boundaries

 commonbounds R Documentation

## Commonly Used Group Sequential Boundaries

### Description

'commonbounds' determines group sequential boundaries of the well-known O'Brien-Fleming and Pocock types. These can be used as guidelines for early stopping of the trial. For Haybittle-Peto type boundaries, see function 'lastbound'. Note: these are NOT the alpha-spending versions of these boundaries.

### Usage

``````commonbounds(looks, t=(1:looks)/looks, t2=t, iuse="OF", alpha=0.05, sides=2)
``````

### Arguments

 `looks` A number of equally spaced analysis times. `t` a vector of analysis times, if `looks` is not provided. If times are provided and they are not equally spaced, there will be a warning. `t2` the second time scale, usually in terms of amount of accumulating information. By default, same as the equally spaced analysis times or the analysis times corresponding to `t`. `iuse` the type of bounds: O'Brien-Fleming ("OF") or Pocock ("PK") If two-sided bounds are calculated, the same type will be used for each of the two boundaries. If a vector of length two is given, the two values will be used for lower and upper bounds, respectively. Details of specification are given below. `alpha` Type I error(s). In two-sided situations, alpha can be a single value, indicating symmetric type I error control (half of alpha for each boundary). If a vector of length two is given, this corresponds to the amount allocated to the lower and upper boundaries, respectively. The total alpha must be greater than 0 and less than or equal to 1. `sides` Designates one- or two-sided bounds.

### Details

This function calculates boundaries corresponding to traditional O'Brien-Fleming or Pocock boundaries. Note that these are not the alpha spending function versions of the boundaries. For those, use `ldBounds`.

### Value

'commonbounds' returns an object of 'class' '"ldBounds"'.

For details about this object class, see the documentation for the `ldBounds` function.

### Author(s)

Charlie Casper charlie.casper@hsc.utah.edu

### References

Reboussin, D. M., DeMets, D. L., Kim, K. M., and Lan, K. K. G. (2000) Computations for group sequential boundaries using the Lan-DeMets spending function method. Controlled Clinical Trials, 21:190-207.

DeMets, D. L. and Lan, K. K. G. (1995) Recent Advances in Clinical Trial Design and Analysis, Thall, P. F. (ed.). Boston: Kluwer Academic Publishers.

Lan, K. K. G. and DeMets, D. L. (1983) Discrete sequential boundaries for clinical trials. Biometrika, 70:659-63.

Generic functions `summary.ldBounds` and `plot.ldPower`.

`ldBounds` for boundaries that use the alpha spending approach.

`ldPower` for exit probabilities given boundaries OR drift (effect) given power OR confidence interval OR adjusted p-value.

### Examples

``````   ## From Reboussin, et al. (2000)

time <- seq(0.2,1,length=5)
obf.bd <- commonbounds(t=time)
summary(obf.bd)
plot(obf.bd)

# Equivalent bounds to above
obf.bd2 <- commonbounds(5)

``````

ldbounds documentation built on June 22, 2024, 6:53 p.m.