Suppose a new study is planned, with 200 patients randomly assigned to each of a 400 IU per day vitamin E group and a 3 IU per day vitamin E group. If the survival experience in the 3 IU per day group is assumed the same as in Table 14.33, the relative hazard for the 400 IU/day group vs. the 3 IU/day group = 1.5, and the censoring experience of both groups are assumed the same as for the 3 IU per day group in Table 14.33, then how much power would a new study have if the maximum duration of follow-up is 4 years (rather than 6 years as in the original study) and a two-sided test is used with α = .05? 

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