Nominal, Ordinal, Interval and Ratio Scales Of Measurement

When conducting a study, we normally collect relevant data for it. These data may be different in types and nature. Each type of data has its own merits and demerits. Therefore, we adopt  separate statistical approach or method for analyzing and interpreting each distinct type of data, because we can’t efficiently handle each and every type of data with the same statistical approach or method. But if we do so, either intentionally or unintentionally, then our study may give us invalid results. Therefore, it should be kept in mind that types of data play an important role in shaping all our research activities. Normally we categorize data into four distinct levels or classes. These classes or levels of data are called scales of measurement. They are: nominal, ordinal, interval and ratio.

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Ratio Scale Of Measurement

Ratio is the fourth scale of measurement. It is considered to be the best among all the four scales of measurement as it satisfies all the properties needed for a perfect scale i.e. each value on this scale has a unique meaning, all the  values on this scale can be arranged in proper order,  the interval among its different values can be accurately measured and it has absolute zero, there is no value below zero on this scale. Weight is a simple example of this scale. It has unique values ; the interval between any two values of it can be easily and accurately measured; and zero weight means no weight. Similarly height is another example of ratio.  Still another example is scores on a particular test. Here each score represents unique value; the interval among different scores can be precisely calculated; and zero score means no score.  Ratio is the most powerful scale of measurement as various powerful statistical tools can be easily applied on it. You can best understand this scale by comparing it with the other three scales of measurement: nominal, ordinal and interval.

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