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Table 3 Power (%) to detect a difference between BT and nBT groups in Randomisation A

From: Protocol, rationale and design of SELPHI: a randomised controlled trial assessing whether offering free HIV self-testing kits via the internet increases the rate of HIV diagnosis

Diagnosis rate in nBT group (%)

Diagnosis rate in BT group (%)

50

60

70

80

20

91

99

100

100

30

53

83

96

99

40

16

45

75

92

50

5

14

39

68

  1. Power to detect a difference at 2α = 0.05 by chi-squared test
  2. Assumes seroprevalence rate = 2%