What is ratio data?

Ratio data are continuous data where both differences and ratios are interpretable. Ratio data has a natural zero. A good example is birth weight in kg.

The distinctions between interval and ratio data are subtle, but fortunately, this distinction is often not important. Certain specialized statistics, such as a geometric mean and a coefficient of variation can only be applied to ratio data.

Example: In the discussion of the use of a Visual Analog Scale for present functioning of children or adolescents, researchers argued that the VAS possessed properties of a ratio scale.

Price et al. have investigated the measurement properties of the VAS in a series of psychophysical studies, demonstrating that the VAS has ratio rather than interval scale properties [29]. Thus, in addition to properties of interval scales which reflect equal distances in the variables being quantitatively ordered, the ratio scale indicates a true zero point [30]. -- The PedsQL™ Present Functioning Visual Analogue Scales: preliminary reliability and validity. Sandra A Sherman, Sarajane Eisen, Tasha M Burwinkle, and James W Varni. Health and Quality of Life Outcomes 2006, 4:75doi:10.1186/1477-7525-4-75. [Medline] [Abstract] [Full text] [PDF]

This work is licensed under a Creative Commons Attribution 3.0 United States License. It was written by Steve Simon on 2002-10-11, edited by Steve Simon, and was last modified on 2008-01-11. This page needs major revisions. Category: Definitions.