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Table 1 Sample size in each site to give the required expected number of events under different scenarios using eqn ( 6)

From: Sample size calculation for multicentre efficacy trials of blood-stage malaria antigens

Centres % malaria after six months Sample size (all the required number can be recruited) No of events [eqn( 6)] Sample size (only 70% can be recruited) No of events [eqn( 6)]
Scenario 1: Sample size of 460 in each site with the best estimate of incidence rates
A 0.1 460 33 322 23
B 0.3 460 102 322 71
C 0.3 460 102 322 71
D 0.3 460 102 322 71
Total   1,840 339 1,288 237
Scenario 2: Very low incidence in centre A
A 0.05 460 17 322 12
B 0.3 460 102 322 71
C 0.3 460 102 322 71
D 0.3 460 102 322 71
Total   1,840 322 1,288 226
Scenario 3: Very low incidence in both centres A and B
A 0.05 460 17 322 12
B 0.05 460 17 322 12
C 0.3 460 102 322 71
D 0.3 460 102 322 71
Total   1,840 237 1,288 166
Scenario 4: All sites have incidence reduced to half
A 0.05 460 17 322 12
B 0.15 460 50 322 35
C 0.15 460 50 322 35
D 0.15 460 50 322 35
Total   1,840 168 1,288 117
Scenario 5: Centre D drops out of the study
A 0.1 460 33 322 23
B 0.3 460 102 322 71
C 0.3 460 102 322 71
Total   1,380 237 966 166