Sample size calculations I

A randomised, double blind, placebo controlled trial investigated whether fluvastatin reduced major adverse cardiac events in patients who had undergone successful percutaneous coronary intervention (with or without stenting). The primary outcome was the occurrence of major adverse cardiac events—defined as cardiac death, non-fatal myocardial infarction, or a reintervention procedure—within three years.1 To calculate the sample size needed to compare fluvastatin with placebo, it was assumed that the proportion of patients having major adverse cardiac events at three years without treatment would be 25%. For fluvastatin to be considered clinically superior to placebo, it would be necessary to demonstrate a relative improvement of 25%, with only 18.75% of patients having major adverse cardiac events at three years. To do so, a total sample size of 1828 patients (914 in each treatment arm) would be required to achieve 90% power using a two sided hypothesis test and critical level of significance of 0.05. A total of 1677 patients were subsequently recruited to the trial. Which of the following, if any, are true?