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Table 2 Required Sample Size for Intermediate-Risk Group Patients with Two Interim Analyses

From: Statistical design of Phase II/III clinical trials for testing therapeutic interventions in COVID-19 patients

Required Sample Size for Intermediate-Risk Group Patients with Two Interim Analyses
Effect size   α = 0.05 with 1:1 Group Ratio α = 0.05 with 1:2 Group Ratio
Power 80% 90% 80% 90%
10% N1 315 438 235 326
N2 315 438 470 652
Total 630 876 705 978
15% N1 140 194 104 145
N2 140 194 208 290
Total 280 388 312 435
20% N1 78 108 58 81
N2 78 108 116 162
Total 156 216 174 243
25% N1 49 67 37 51
N2 49 67 74 102
Total 98 134 111 153
30% N1 33 45 25 35
N2 33 45 50 70
Total 66 90 75 105
35% N1 23 32 18 25
N2 23 32 36 50
Total 46 64 54 75
40% N1 17 23 13 18
N2 17 23 26 36
Total 34 46 39 54
  1. N1: sample size for the standard care arm. N2: sample size for the treatment arm
  2. Response rate = 40%
  3. For 80% power: probability of rejection at each look: 1st look p < 0.002, futility look p > 0.835, 2nd look p < 0.014, futility look p > 0.312, final look p < 0.046
  4. For 90% power: probability of rejection at each look: 1st look p < 0.002, futility look p > 0.830, 2nd look p < 0.014, futility look p > 0.298, final look p < 0.046
  5. ρ = 3.0
  6. Bold indicates recommended sample size with suggested parameters