Types of Scales in Statistics
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Types of Scales in Statistics


Community Dentistry


[C.R. Kothari 2nd ed 71]
Data is classified into quantitative and qualitative data.
Qualitative data can be nominal or ordinal and quantitative data can be discrete (often, integer) or continuous.

Nominal scale data

a) The information is divided into some definite qualitative basis.


  • Male/ female
  • White/ black
  • Urban / Sub-urban / Rural
  • Age
  • Socioeconomic status
Ordinal scale data

a) Information is expressed in ordinal or rank order relations.


  • Olympic medals
  • Ranking of medical students

b) For example, Ramu is taller than Ravi and Ravi taller than Vijay, we know something.

The information gives the difference in quality but not quantity. No conclusion can be drawn about whether the height difference between Ramu and Ravi is same as the difference between Ravi and Vijay.

Interval or numeric scale data

a)Uses a scale graded in equal increments

Eg:  Height, weight, blood pressure.

b) For example the difference between 2nd and 3rd inches is same as the difference between 7th and 8th inches.

c) If a measurement has a ''mean" and a "standard deviation", it can be treated as interval scale.

Ratio scale data

a) The interval scale data is placed with some meaningful ratio,


  • Weight
  • Time
  • Blood pressure
  • Temperature measured in degrees
  • Kelvin

b) This type of data is biomedically most


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