In 1967, Millichap and Fowler1 published a valuable review of the available literature studying drug treatment of hyperkinetic children. They broke down the adequately controlled studies into several tables. They further digested the information by combining and averaging the results from many studies to get the average percentages improved with each drug. Using these percentages, they listed the drugs in the order of apparent efficacy as "the closest approximation possible with the evidence available." At the head of the list, with 83% improvement, was methylphenidate hydrochloride (Ritalin). Next came dextroamphetamine sulfate (Dexedrine) with 69% improvement.
The casual reader might jump to the conclusion that methylphenidate's superiority to dextroamphetamine had been established. However, the rest of the article had already made it clear that these two percentages were based on separate studies of different drugs by different investigators on different population samples with different dosages and different criteria of improvement.
Arnold LE, Knopp W. The Making of a Myth. JAMA. 1973;223(11):1273-1274. doi:10.1001/jama.1973.03220110051016