Definición Level of measurement

In statistics, depending on the kind of data we ascertained, we use different kinds of scales. Not every attribute or variable can be translated to numerical values in the same way. While body size can easily be depicted in centimeters or in feet and inches, this is not possible for variables such as gender and possible but difficult for levels of personal satisfaction.

The level of measurement expresses, how quantifiable a value actually is, i.e. to what extend we can apply mathematical operations. We differ four levels of measurement:

• nominal scale (non-metric or categorical)
• ordinal scale (non-metric or categorical)
• interval scale (metric)
• ratio scale (metric)

The nominal scale offers the least statistical information content, the ratio scale the highest. Nominal and ordinal are non-metric or categorical scales, that is, their response values are not directly usable as a numerical value. Interval and ration scales are metric scales that allow for various arithmetic operations. Examples:

Nominal scale:

• gender (male, female)
• color (blue, yellow, red, green, etc.)

Ordinal scale

• type of residence (single house, village, town, city)
• category of vehicle (compact car, medium-sized vehicle, luxury car, etc.)

Interval scale

• temperature in Celsius
• IQ scale

Ratio scale

• body height
• monthly income

A summary: