Types of Data and Measures of Central Tendency
Describing Variables
Another important distinction between variables is whether the variable is a qualitative variable or a quantitative variable.
Qualitative Variables are those which are measured by quality, rather than quantity. Qualitative variables can be further broken down into:
- Nominal Variables: simply named categories (such as hair color, gender, religion)
- Ordinal Variables: a set of ordered categories, which can not be subdivided (an example is cancer staging i.e. Stage I vs. Stage II)
Quantitative Variables are variables that are measured in terms of numbers. An example of a quantitative variable in the hypertension study is the dosage of medication the patients received (e.g. 5mg or 10 mg or 20 mg).
This distinction is important because the way one summarizes and describes data differs depending on the type of variable that makes up the data. This will be explained in further detail in subsequent sections of this module.