Levels of Measurement and Their Importance

Levels of Measurement and Their Importance

• Source: Salkind, Tests and Measurement 3e. SAGE Publishing (2018)

Introduction to Variables and Measurement

• What is a variable?
  • A variable is any characteristic, number, or quantity that can be measured or counted.
• What is measurement?
  • Measurement is the process of assigning numbers or labels to variables to represent quantities or qualities.

Historical Context: S.S. Stevens (1946)

• Stevens was pivotal in exploring how different types of variables could be measured.
• He raised several questions:
  • How are different types of variables measured?
  • Does the level of precision in measurement aid in the classification of variables?
  • Can a system be created to classify outcomes based on the characteristics of these variables?

Importance of Measurement

• Key Concept: Variables can be measured in different ways.
• The method of measurement determines the level of measurement being employed.
• Example:
  • Height:
  • Group 1 taller than Group 2 (ranking or magnitude)
  • Distinction based on the number of inches provides more precision and detail.

Levels of Measurement

• Definition: The levels of measurement indicate how much information is conveyed by the outcome measure.
• There are four levels of measurement:
  1. Nominal
  2. Ordinal
  3. Interval
  4. Ratio

Nominal Level of Measurement

• Characteristics:
  • Differences are based on quality rather than quantity.
  • Categorical or discrete, focusing on qualitative information (