Organizations have become increasingly aware of making good selection decisions. Attracting a large number of individuals will be of little use unless there is a way of measuring how individuals differ. People can differ in many ways such as intelligence, attitudes, social skills, physical characteristics, experience and so on. Selection techniques should meet these principles of measuring differences and predicting performance to varying degree. So it is imperative as an HR professional to have a sound knowledge of measuring and interpreting individual differences.
Rigorous measurement is a prerequisite in selection, because our ability to distinguish from one person to another is determined by the precision with which we can measure the variables. In this context various types of scales of measurement are used. Scales of measurement is simply a means by which individuals can be distinguished from one another. Four types of scales of measurement exist: 1. Nominal 2. Ordinal 3. Interval and 4.Ratio. Nominal scale is one which is composed of two or more mutually exclusive categories. In nominal scale all individual having a common characteristics are assigned the same category or class. An ordinal scale is one which ranks objects, such as individuals from high to low on some variable of interest. For instance supervisors may be asked to rank their subordinates with respect to some characteristics like performance. Another example of ordinal scale often encountered in selection involves test scores. Percentiles are sometimes used to interpret the results of a test. With an interval scale differences between numbers take on meaning. In addition to rank order information scale uses constant units of measurement, affording a meaningful expression of differences with respect of characteristics. Interval scale has an arbitrary and not an absolute zero point. As on the interval scale, differences between