New advances in healthcare are introduced everyday and the wealth of information can be overwhelming.

There are many methods of describing the measure of effectiveness of new interventions in ways that aim to help patients, prescribers and policy-makers understand the relative benefits and harms of these treatments and make informed decisions.

One of these methods is to calculate how many patients would need to be treated with a drug, in order for ONE of them to show the desired effect. This value is known as the number needed to treat, or the NNT.