This histogram shows the sizes of all RCTs in head injury published before 1998.

- 62 trials had fewer than 20 patients

- Only 8 trials were large enough to detect an absolute reduction in the risk of death or disability of 10%

- And no trials were large enough to detect a 5% absolute reduction

- Therefore, to reliably detect clinically important treatment effects of a few percent, we need a study with thousands of patients…