Important: Please read the Technical Considration section of
Sample Size for Phase II Study (Simon's Procedure) Explained and Tables Page
before using the results of calculations from this program
Abbreviations
- π0 = proportion of success at or below which treatment is abandoned
- π1 = proportion of success at or above which treatment will be accepted for
further development and trials
- n1 = maximum sample size required in stage 1
- r1 = number of successes above which stage 2 can be entered, and at or below
which when n1 cases is reached the trial ends and the treatment abandoned.
- nTot = the total maximum sample size (stage 1 and 2 combined)
- rTot = the total number of successes (stage 1 and 2 combined) above which
the study can be terminated and the treatment accepted for further development and trials, and at or
below which when nTot cases is reached the treatment is abandoned.
- EN = expected sample size, an estimated average sample size that will be used
before the trial terminates. This is a measure of efficiency in detecting
useful treatments
- PET = probability of early termination (when treatment is abandoned), a measure
of efficiency in rejecting ineffective treatments.
- The table was calculated using α (probability of Type I Error) of 0.05 and power (1-β) of 0.8,
β being probability of Type II Error.
Models
- Minimax : the model to be used when the treatment is expected
to be useful and accepted for Phase III trial, as it has smaller sample size
in stage 1 and a lower EN, so more quickly to enter stage 2 and terminate
with acceptance of treatment.
- Optimal : the model that should be used when the treatment is
expected to be rejected, as it has a higher PET, so more likely to be rejected
earlier if the success rate is less than expected.
References
Simon R (1989) Optimal two-stage designs for phase II clinical trials.
Control Clin Trials 10:1-10
Machin D, Campbell M, Fayers, P, Pinol A (1997) Sample Size Tables for
Clinical Studies. Second Ed. Blackwell Science IBSN 0-86542-870-0 p. 256-257
