Sample size, randomization and masking
BLIND
A sample of 40 adults was needed to provide 80% power to detect clinically meaningful improvements in performance, using a two-tailed test with alpha = 0.05. An independent research nurse at Centre for Clinical Research, County of Västmanland, generated a simple randomization list. An independent pharmacist labelled and blinded the study medication. The pills were identical in appearance and placed in two bags marked “Day 1” and “Day 2.” The two bags, along with a smaller opaque, sealed envelope containing the identification of the assigned group, were placed in a sealed sequentially numbered identical envelope, one for each participant. The smaller envelope was opened after the participant had completed the study by a medical professional not involved in the study. Neither the research nurse who produced the randomization schedule nor the pharmacist participated in any other aspect of the study. Both investigators and participants were blind to treatment allocation.