StatsToDo : Sample Size for Phase II Study (Simon's Procedure)
Program
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.
 Probability of Type I Error (α) Power (1 - β) Proportion to reject treatment (π0) Proportion to accept treatment (π1)

### 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