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Table 2 Sample size assuming 5 % level of significance, 90 % power, 50 % relative risk reduction

From: A study of an intelligent system to support decision making in the management of labour using the cardiotocograph – the INFANT study protocol

Incidence of primary outcome in ‘no decision-support’ group Incidence of primary outcome in ‘decision-support’ group Relative risk Total sample size required
3 per 1000 1.5 per 1000 0.5 46,000
4 per 1000 2 per 1000 0.5 34,000
5 per 1000 2.5 per 1000 0.5 27,000
6 per 1000 3 per 1000 0.5 22,000