Question

A study was performed among patients with progressive chronic kidney disease to assess the optimal time for the initiation of dialysis (Cooper et al. [22]). Patients were randomized to either

1. an early start group, where dialysis was initiated when their estimated glomerular filtration rate (GFR) was between 10.0 and 15.0 mL per minute per 1.73 m2 of body surface area or
2. a late start group, where dialysis was initiated when their GFR was 5.0 to 7.0 mL per minute per 1.73 m2 of body surface area.

The primary outcome was total mortality. There were 404 patients assigned to the early start group, of whom 152 died. There were 424 patients assigned to the late start group, of whom 155 died over the same time period. Patients were enrolled from July 2000 to November 2008 and were followed for 3 years.

What test can be used to compare the mortality rates in the two groups? Report a two-sided p-value.

Answer 1

Solution: Here concept of z-test for equality of two population proportions is used.

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