Decrement table


Decrement tables, also called life table methods, are used to calculate the probability of certain events.

Birth control

methods are often used to study birth control effectiveness. In this role, they are an alternative to the Pearl Index.
As used in birth control studies, a decrement table calculates a separate effectiveness rate for each month of the study, as well as for a standard period of time. Use of life table methods eliminates time-related biases, and in this way is superior to the Pearl Index.
Two kinds of decrement tables are used to evaluate birth control methods. Multiple-decrement tables report net effectiveness rates. These are useful for comparing competing reasons for couples dropping out of a study. Single-decrement tables report gross effectiveness rates, which can be used to accurately compare one study to another.

Footnotes