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Table 1 Odds ratios detectable for given exposure variable frequencies1

From: The UK Midwifery Study System (UKMidSS): a programme of work to establish a research infrastructure to carry out national studies of uncommon conditions and events in midwifery units

Exposure variable frequency in control group

Odds ratio detectable by the study

5 %

≥1.7

10 %

≥1.5

15 %

≥1.4

20 %

≥1.3

30 %

≥1.3

50 %

≥1.3

80 %

≥1.4

  1. 1 80 % power at p < 0.05