This tool searches for Simon (1989) two-stage Phase II designs meeting your target Type I error and power, and reports the minimax design (smallest maximum sample size) and the optimal design (smallest expected sample size under the null) found within your search range.

Input Parameters

This calculator helps determine optimal or minimax two-stage designs for phase II clinical trials, allowing early termination for futility.

Minimum Stage 1 Sample Size Value between 1 and 500

Maximum Stage 1 Sample Size Value between 1 and 500

Maximum Total Sample Size Value between 2 and 500

Probability under null hypothesis (p₀) Value between 0 and 1

Probability under alternative hypothesis (p₁) Value between 0 and 1

Maximum Alpha Type I error rate

Minimum Power (1 − β) Value between 0 and 1

Results

How to use this design:

Enroll N1 patients in Stage 1
Count the number of responses (x1) in Stage 1
If x1 ≤ n1, stop the trial and conclude the treatment is ineffective
If x1 > n1, continue to Stage 2 and enroll an additional (N − N1) patients
Count the total number of responses (x) across both stages
If x > n2, conclude the treatment is effective; otherwise, conclude it is ineffective

Design Types:

Minimax Design: Minimizes the maximum possible sample size needed
Optimal Design: Minimizes the expected sample size under the null hypothesis

How to use this design:

Related Tools