- Categorical variables
- Categorical variables are also called qualitative variables or attribute variables. The values of a categorical variable are mutually exclusive categories or groups. Categorical data may or may not have some logical order.
- Quantitative variables values of a quantitative variable are numbers that usually represent a count or a measurement.
Often, you will collect both categorical data and quantitative data when exploring a single subject. Categorical variables are often used to group or subset the data in graphs or analyses. Here are some examples of categorical and quantitative data that you could collect when exploring the same subject:
| Subject of the analysis | Possible categorical variables | Possible quantitative variables |
|---|---|---|
Household appliance sales
|
Type of appliance; Make and model
|
Sale price
|
Automobile body painting
|
Paint flaws (peel, scratch, smudge, other); Paint colors
|
The temperature of the metal to be painted; Thickness of the paint layer
|
Quantitative variables
Categorical variables
Characteristics of Categorical and Quantitative data:
Class of measurement:
- Quantitative data belong to ordinal, interval, or ratio classes of measurements.
- Categorical data belong to the nominal class of measurements.
Methods:
- Methods used to analyze quantitative data are different from the methods used for categorical data, even if the principles are the same, at least the application have significant differences.
Analysis:
- Quantitative data are analyzed using statistical methods in descriptive statistics, regression, time series, and many more.
- For categorical data, usually descriptive methods and graphical methods are employed. Some non-parametric tests are also used.
