Analysis of quantitative data by quantiles in epidemiologic studies: classification according to cases, noncases, or all subjects?

Epidemiology. 1991 Mar;2(2):137-40. doi: 10.1097/00001648-199103000-00008.


Quantitative exposure data in epidemiologic studies are frequently analyzed by ordered categories. Categorization by quantiles can be based on the distribution of (1) cases, (2) noncases, and (3) all subjects. The advantages of the three schemes in determining quantiles were compared. They were found to give the same power regarding a test for trend over a wide range of study situations. Considerations on the representativeness and the ease of the analysis implementation could dictate the choice of the categorization scheme.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Case-Control Studies
  • Classification*
  • Cohort Studies
  • Data Interpretation, Statistical*
  • Epidemiologic Methods*
  • Humans
  • Odds Ratio