Types of Data and Sampling

Categorical vs. Quantitative Data

Data can be classified into two main types:

Categorical (Qualitative) Data describes qualities or characteristics. Examples include eye color, zip code, or political party. Categorical data can be:

• Nominal: No natural ordering (e.g., blood type: A, B, AB, O)
• Ordinal: Has a natural order (e.g., satisfaction: low, medium, high)

Quantitative (Numerical) Data represents measurable quantities. It can be:

• Discrete: Countable values (e.g., number of siblings: 0, 1, 2, 3…)
• Continuous: Any value in a range (e.g., height: 5.7 ft, weight: 150.3 lbs)

Individuals and Variables

• Individuals are the objects described by a set of data (people, animals, things)
• Variables are characteristics of an individual

Levels of Measurement