The extent to which a specific intervention, procedure, regimen, or service produces a beneficial result under ideal conditions. Ideally, the determination of efficacy is based on the results of a randomized control trial.
The extent to which an intervention can be shown to be beneficial under optimal conditions.
Commonly used synonymously with effectiveness , but may usefully be distinguished from it by using efficacy for the results of actions undertaken under ideal circumstances and effectiveness for their results under usual or normal circumstances. Actions can thus be efficacious and effective, or efficacious and ineffective, but not the reverse.
The ability to produce a desired effect.
In scientific research, a treatment’s efficacy is its power to obtain a desired effect, such as reducing pain.