Comparing proportions an example

A randomized trial in advanced colorectal cancer was designed to compare response rates in patients allocated fluorouracil and leucovorin (FUFA), with or without interferon a (IFN). The response rate for FUFA was expected to be approximately 30 per cent, and the study was powered to detect a 20 per cent absolute increase (to 50 per cent) through the use of IFN with 80 per cent power and a 2-sided significance level of 5 per cent. Using equation 5.4 and Table 5.2, the number of patients required in each group was {7.849 x [(0.3 x 0.7) + (0.5 x 0.5)]}/0.22 = 91, i.e. a total sample size of approximately 182 patients.

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