13th February 2024

In a study of 5,000 patients, 500 out of 2,500 participants in the control group suffered at least one migraine at two months when taking a placebo drug.

In a study of 5,000 patients, 500 out of 2,500 participants in the control group suffered at least one migraine at two months when taking a placebo drug. 100 out of 2,500 participants in the experimental arm trialling a new prophylactic drug suffered at least one migraine at two months. 

Calculate the number needed to treat to prevent one migraine episode (to the nearest whole number).