Simulate safety stopping values. The effect can be given as proportion of events in the experimental group (pH1), the risk difference (rdH1), risk ratio (rrH1) or odds ratio (orH1).

Source: R/sim_safety_stop.R

Simulate safety stopping values. The effect can be given as proportion of events in the experimental group (pH1), the risk difference (rdH1), risk ratio (rrH1) or odds ratio (orH1).

simSafetyStop(
  nevents,
  pH0 = 0.5,
  alpha_test = 0.025,
  pH1 = NULL,
  rrH1 = NULL,
  orH1 = NULL,
  rdH1 = NULL,
  r0 = NULL,
  n = NULL
)

Arguments

nevents

vector with number of events at which an interim analysis is done

pH0

proportion of events in the experimental arm under the null hypothesis, typically based on randomization ratio (e.g. 0.5 for a 1:1 randomization)

alpha_test

nominal alpha level for binomial exact test

pH1

proportion of events in the experimental arm under the alternative hypothesis

rrH1

risk ratio (experimental / control).

orH1

risk ratio (experimental / control). Requires the control proportion (r0).

rdH1

risk difference (experimental - control). Requires the control proportion (r0) and the number of participants (n).

r0

risk in the control group. Required if the effect is given as risk difference or odds ratio.

n

total number of participants. Required if the effect is given as risk difference.

Value

list with a dataframe with number of events in each group plus upper limit for stopping and indicator for whether stopped, plus indicators number of stops and time points at first stop

Examples

set.seed(1)  
simSafetyStop(nevents=seq(10,100,by=10),pH0 = 0.5, pH1 = 0.6,alpha_test=0.025)
#> $tests
#>    nevents n1 n0 ulim   out
#> 1       10  5  5    9 FALSE
#> 2       20 10 10   15 FALSE
#> 3       30 17 13   21 FALSE
#> 4       40 23 17   27 FALSE
#> 5       50 27 23   33 FALSE
#> 6       60 35 25   39 FALSE
#> 7       70 41 29   44 FALSE
#> 8       80 46 34   50 FALSE
#> 9       90 53 37   55 FALSE
#> 10     100 57 43   61 FALSE
#> 
#> $nstop
#> [1] 0
#> 
#> $tstop
#> [1] NA
#> 

set.seed(1)  
simSafetyStop(nevents=seq(10,100,by=10),pH0 = 0.5, rrH1 = 0.6/(1-0.6), alpha_test=0.025)
#> $tests
#>    nevents n1 n0 ulim   out
#> 1       10  5  5    9 FALSE
#> 2       20 10 10   15 FALSE
#> 3       30 17 13   21 FALSE
#> 4       40 23 17   27 FALSE
#> 5       50 27 23   33 FALSE
#> 6       60 35 25   39 FALSE
#> 7       70 41 29   44 FALSE
#> 8       80 46 34   50 FALSE
#> 9       90 53 37   55 FALSE
#> 10     100 57 43   61 FALSE
#> 
#> $nstop
#> [1] 0
#> 
#> $tstop
#> [1] NA
#>