Multiple significance tests: the Bonferroni correction

Researchers assessed the effects of hormone replacement therapy, consisting of combined oestrogen and progestogen, on health related quality of life. A randomised placebo controlled, double blind trial study design was used. Women were recruited if they were postmenopausal, had a uterus, and were aged 50-69 at randomisation. Outcome measures included health related quality of life and psychological wellbeing. The study period was one year.1 The researchers investigated the effects of combined hormone replacement therapy compared with placebo at one year, using a 0.05 (5%) critical level of significance and adjusting this with the Bonferroni correction. The researchers concluded that combined hormone replacement therapy started many years after the menopause can improve health related quality of life. For which of the following does the Bonferroni correction reduce the probability of occurring? The Bonferroni correction reduces the …