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Effectiveness vs Efficacy


  • ‘Effectiveness’ (noun) refers to the degree to which something is successful in producing a desired result.
  • ‘Efficacy’ (noun) refers to the ability of something to produce a desired or intended result.

What’s the difference between ‘effectiveness’ and ‘efficacy’?

Because they are superficially similar in meaning, these two words can be used interchangeably in research papers. But in some specific cases and fields of research, they can mean different things.

  • In Medicine, for instance, ‘efficacy’ is the degree of success of a treatment or method under ideal and controlled circumstances, while ‘effectiveness’ is how well it performs in the real world.
  • Due to its technical meaning, the use of ‘efficacy’ tends to be confined to the medical field. On the other hand, ‘effectiveness’ has much broader uses across disciplines.

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How they’re used

Example sentences with ‘effectiveness’

  • The policy has already demonstrated its effectiveness in reducing crime.
  • The treatment has demonstrated its effectiveness in curing patients.

Example sentences with ‘efficacy’

  • The efficacy of the drug is measured through various assessment scales.
  • The trials were based on evidence of potential efficacy in animals.