See treatment effects.

Occurs when the person who is enrolling a participant into a clinical trial is unaware whether the next participant to be enrolled will be allocated to the intervention or control group.

A study which involves identifying patients who have the outcome of interest (cases) and patients without the same outcome (controls), and looking back to see if they had the exposure of interest.

A report on a series of patients with an outcome of interest. No control group is involved.

A systematically developed statement designed to assist clinician and patient decisions about appropriate health care for specific clinical circumstances.

Involves identification of two groups (cohorts) of patients, one which received the exposure of interest, and one which did not, and following these cohorts forward for the outcome of interest.

Quantifies the uncertainty in measurement. It is usually reported as a 95% CI which is the range of values within which we can be 95% sure that the true value for the whole population lies. For example, for an NNT of 10 with a 95% CI of 5 to 15, we would have 95% confidence that the true NNT value lies between 5 and 15.

See treatment effects.

Assesses whether the cost of an intervention is worth the benefit by measuring both in the same units; monetary units are usually used.

Measures the net cost of providing an intervention as well as the outcomes obtained. Outcomes are reported in a single unit of measurement.