Table 3 Power calculation for changes in practice for various assumptions of % with practice pre-intervention – p₁ (20–60%), p₂ (30–90%), assuming 80% power at 5% level of statistical significance (2-sided test), for sizes of effect ≤ 2 and for cluster size three (numbers of babies admitted per hospital)

p ₁

P ₂

30

35

40

45

50

55

60

65

70

75

80

85

90

60

0.14

55

0.01

0.6

50

0.07

0.54

45

0.06

0.5

40

0.06

0.5

35

0.07

0.5

30

0.1

0.54

25

0.14

0.6

20

0.2