Definition: The Ratio Scale is the highest level scale that allows the researcher to classify or identify the objects, rank-order the objects and compare the intervals or differences.
The ratio scale possesses all the characteristics of nominal, ordinal and interval scale and in addition to it, it also possesses a true zero point or origin characteristic. With a zero point, it is possible to calculate the ratios of the scale values. The most common examples of ratio scales are weight, age, height, and money. In the case of marketing research, sales, market share, price, and number of consumers are measured on a ratio scale.
These are the most informative scales as it tells about the order and the number of objects between the values of the scale. The ratio scales allow the researcher to apply any statistical technique, including, geometric mean, harmonic mean, and coefficient of variation. Also, the central tendency can be measured by using either of the statistical tools, Viz. Mean, Median, Mode.
The ratio scales offer only the proportionate transformation of the form y = bx, where b= positive constant. The arbitrary constant cannot be added, as in the case of the interval scale. This transformation can be explained through an example of conversion of a centimeter to millimeter (b =10). It is to be noted that the comparison between the objects will be identical whether made in centimeter or millimeter.