In statistics and math there are two types of data: quantitative data and categorical data. A variable that represents quantitative data is called a quantitative variable while a variable representing categorical data is called a categorical variable.
Overview: What is a quantitative variable?
Quantitative data represents values and numbers which can be measured or counted and used in mathematical operations such as addition, subtraction, multiplication, or division. Quantitative variables can be further separated into discrete and continuous variables.
Continuous variables represent the value you get when you measure something with a measuring device such as a scale, tape measure, stopwatch, etc. A continuous variable can take on any value over a continuum of possible values and can be logically subdivided given the resolution of the measuring device.
By contrast, discrete variables are counted, not measured. You can have 5 people, 10 boxes, or 10 invoice errors. It makes no sense to talk in terms of 5.3 people or 10.636 errors on an invoice. In both cases, continuous and discrete variables can be used in mathematical operations.
An industry example of a quantitative variable
The shipping department of a company wanted to capture data on its on-time delivery performance to its customers. One person wanted to just collect whether the order was delivered on time or not. The company Black Belt (BB) wanted to collect the exact time the order was delivered to see if there were any trends.
The company Master Black Belt (MBB) agreed so the delivery driver started to collect the actual time of delivery. This type of data was quantitative versus the suggestion of categorical.
Frequently Asked Questions (FAQ) about a quantitative variable
What is the difference between a quantitative and categorical variable?
A quantitative variable represents values that are measured or counted. Categorical variables represent groupings of some kind. They are sometimes recorded as numbers, but the numbers represent categories rather than actual amounts of things. An example would be tossing a coin and counting the number of heads and tails.
How many values can a quantitative variable have?
A quantitative variable can take on as many values as the resolution of the data allows.
Why are quantitative variables preferred over categorical variables?
There is much more granularity in a measured variable such as the length of time it takes to complete a task versus just recording whether the task was done or not.