Classification of variables
In this article we shall explore different types of data. In statistics you’ll be required to carry out observations and measurements of information or variables. The observations and measurements that you obtain are known as data. Below is a quick summary of what is covered in this article.
Quick Summary
- Variables associated with non-numerical observations are called qualitative variables.
- Variables associated with numerical observations are called quantitative variables
- A variable that can take any value in a given range is a continuous variable
- A variable that can take only specific values in a given range is a discrete variable.
Types of variables
Below we shall look at the different types of variables. The table below shows a range of variables and their observations.
| Variable | Observations |
|---|---|
| Trouser size | 14, 14½, 15, 15½, 16 |
| Height | 189.8cm, 150cm, 174.4cm |
| Hair colour | Red, Blonde, Brunette |
We classify variables depending on whether their observations can be written down as a number.
- The observations of trouser size are numerical. Therefore the trouser size is called a quantitative variable.
- We can read the number of the height from the observations. The observations of height are numerical therefore height is a qualitative variable.
- The observations of hair colour are not numerical. We therefore say Hair colour is called a qualitative variable
We classify quantitative variables depending on whether their observations are measured on a continuous or a discrete scale.
Quantitative variables
There are two types of quantitative variables; a continuous and discrete variable.
Continuous variable: A continuous variable can take any value in a given range.
Example: Height is a continuous variable because heights of a population sample can be any value in a given range including decimal places. Heights can be any number i.e; 190.8678cm, 200.1cm, 140cm, 132.89cm. Height can be any value in a range we choose to restrict our observations in.
Other examples of continuous variables include;
Other examples of continuous variables include;
| Variable | Example |
|---|---|
| Weight | 50kg, 70kg, 800kg |
| Heart rate | 40bps, 600bps, 5bps |
| Length | 40m, 100m, 200m |
Discrete: A discrete variable will only take specific values in a given range.
Example: Number of cars on the road. You can’t have half a car. Therefore the observations are fixed to a specific values in any range.
| Variable | Classification |
|---|---|
| Time | Continuous |
| Length | Continuous |
| Number of plates | Discrete |
| Weight | Continuous |
| Number of students | Discrete |
