I'm so confused. Not like I'm a doctor, but doesn't the foundational assumption seem fatally flawed? How can you reduce drug efficacy to a single number? It's o

I'm so confused. Not like I'm a doctor, but doesn't the foundational assumption seem fatally flawed? How can you reduce drug efficacy to a single number? It's one thing to compare brands of the same drug, but why in the world are aspirin and acetaminophen (or whatever) just viewed like interchangeable substitutes here? I know I certainly don't reach for the strongest painkiller—but rather the weakest one that might do the job. And I know my doctors certainly never viewed these painkillers as interchangeable. Don't the natures of the effects and side effects actually matter to people?