A technique used to detect differences between groups, which removes bias caused by a separate influential variable, and also has the advantage of increasing precision.

A method for analyzing the differences in the means of two or more groups of cases while taking account of variation in one interval-ratio variable.

In tests of difference among means, an adjustment can be made in advance to “eliminate” or “hold constant” known or suspected background factors that might confound the tests. EX: the effects of a new mouth rinse on plaque scores could be tested after first correcting for baseline plaque scores, DFM, and average dental visits. The variables statistically controlled are known as covariates. An analogue of this technique for measures of association is the partial correlation or hierarchical regression analysis. Performed on statically software, a statistician is helpful. {See templates – Choosing a statistical test.