How many subjects need to be enrolled in each group (assume equal sample size in each group) to achieve 80% power if a two-sided test is used with α = .05 and the same assumptions are made as in Problem 14.20? 

Ophthalmology

In Table 14.33, we present data from the RP clinical trial described in Example 14.30 (on page 813) concerning effect of high-dose vitamin E (400 IU/day) vs. low-dose vitamin E (3 IU/day) on survival (where failure is loss of at least 50% of initial ERG 30 Hz amplitude).

Table 14.33 Number of patients who failed, were censored, or survived by year in the 400 IU vitamin E group and 3 IU vitamin E group, respectively, RP clinical trial

 

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Fail Censored Survive Total 400 IU of vitamin E daily 0-1 уг 1-2 yr 2-3 уг 3-4 yr 4-5 уг 5-6 уг 3 170 180 159 170 159 22 135 24 27 84 135 13 32 39 84 11 28 39 3 IU of vitamin E daily 0-1 уг 169 174 1-2 yr 2-3 yг 3-4 yг 4-5 yг 5-6 уг 10 3 156 169 14 141 156 16 27 98 141 15 34 49 98 0 49 42