diff --git a/DESCRIPTION b/DESCRIPTION index 386bc4f..531531d 100644 --- a/DESCRIPTION +++ b/DESCRIPTION @@ -1,6 +1,6 @@ Package: clinfun Title: Clinical Trial Design and Data Analysis Functions -Version: 1.1.4 +Version: 1.1.5 Depends: R (>= 3.0.0), graphics, stats Imports: mvtnorm Suggests: knitr, rmarkdown, survival diff --git a/NEWS.md b/NEWS.md index 0262dce..04f6ae5 100644 --- a/NEWS.md +++ b/NEWS.md @@ -1,3 +1,7 @@ +# clinfun 1.1.5 (10/19/2023) + +* clarified one-sided vs two-sided futility boundary for gsdesign functions + # clinfun 1.1.4 (10/12/2023) * added check for n; since it is for stopping early at least two values should be given diff --git a/man/gsdesign.Rd b/man/gsdesign.Rd index 373bca9..2963136 100644 --- a/man/gsdesign.Rd +++ b/man/gsdesign.Rd @@ -49,8 +49,10 @@ gsdesign.survival(ifrac, haz.ratio, r = 1, sig.level = 0.05, } \value{ a list with ifrac, sig.level, power, alternative, delta.eb, delta.fb and: - \item{efbdry}{the critical value to use at the different looks.} - \item{futbdry}{the critical value to use at the different looks.} + \item{efbdry}{the critical value to use at the different looks. For + two-sided alternative the absolute test statistic should exceed this.} + \item{futbdry}{the critical value to use at the different looks. For + two-sided alternative the absolute test statistic should be below this.} \item{sample.size}{the sample size per arm for binomial/normal data.} \item{num.events}{the total number of failures which should be converted to number of subjects using censoring proportion.} @@ -59,11 +61,24 @@ gsdesign.survival(ifrac, haz.ratio, r = 1, sig.level = 0.05, The futility boundary is not returned when delta.fb is not specified i.e. stopping for futility is not requested. The futility boundary is non-binding. That is the significance level is not adjusted to account - for early stopping for utility. This makes the test a bit conservative + for early stopping for futility. This makes the test a bit conservative in that the true size is less than the nominal level. + If the alternative is two-sided by default the futility boundary will + also be two-sided i.e. continuation region is wedge shaped. However, + if the goal is to show the superiority of the experimental treatment + then futility boundary should be one sided. This can be achieved by + deriving the boundaries for one-sided alternative and significance + level set at half of the value used for two sided alternative. See the + examples section for a representative design for which the trial + cannot be stopped at the first look for futility. + The Casagrande-Pike-Smith type continuity correction is obtained using the formula \deqn{n*[1 + \sqrt{1+4/(|pC-pE|*n)}]^2} where n is the uncorrected sample size. } +\examples{ + gsdesign.normal(1:4/4, 0.25, sig.level=0.05, alt="t", delta.fb=0.5) + gsdesign.normal(1:4/4, 0.25, sig.level=0.025, alt="o", delta.fb=0.5) +} \keyword{design}