Simple sizes calculation
headache
The sample size was calculated based on the frequency of days with headache outcome, obtaining the highest number of subjects (43 subjects per group), making a total sample of at least 86 subjects. The sample size was calculated using the GRANMO 7.12 program with a α risk of 0.05, two-sided test and a β risk of 0.20. For frequency of headache, an estimated common standard deviation of 4.3 and a minimum expected difference in the follow-up of 2.7, and an estimated dropout rate of 0.07 were used [