The goal of curtailment is to allow users to create single- or two-arm binary outcome clinical trial designs that use a form of early stopping known as stochastic curtailment. Using stochastic curtailment can result in trial designs with a lower sample size on average, compared to typical trial designs or even multi-stage designs. The package contains functions that will search for designs that are suitable for your trial, and draw a diagram showing all points in the trial that a decision may be made to stop early.

You can install the released version of curtailment from CRAN with:

And the development version from GitHub with:

This is a basic example which shows you how to solve a common problem:

```
library(curtailment)
## Find a single-arm design with a maximum sample size in the range 10-25, allowing early stopping after every 5 results, with a type-I error-rate of 0.05 when the response rate equals 0.1 and a power of 0.8 when the response rate equals 0.4:
output <- singlearmDesign(nmin = 10,
nmax = 25,
C = 5,
p0 = 0.1,
p1 = 0.4,
power = 0.8,
alpha = 0.05)
#> | | | 0% | |==== | 6% | |======= | 11% | |=========== | 17% | |============== | 22% | |================== | 28% | |====================== | 33% | |========================= | 39% | |============================= | 44% | |================================ | 50% | |==================================== | 56% | |======================================== | 61% | |=========================================== | 67% | |=============================================== | 72% | |=================================================== | 78% | |====================================================== | 83% | |========================================================== | 89% | |============================================================= | 94% | |=================================================================| 100%
# Obtain the stopping boundaries and a diagram of the above trial:
fig <- drawDiagram(output)
#> n r C alpha power EssH0 Ess thetaF thetaE eff.n
#> 1 20 5 5 0.02288714 0.8588104 11.37274 10.94708 0.3668967 0.92224 20
#> stage
#> 1 4
#> [1] Returning diagram and bounds for single design.
```