Course 1.1Lesson 2 of 3
Data is categorical, in words or labels, or numerical, in numbers. Categorical data is nominal if the labels have no order, such as colour, and ordinal if they have an order, such as shirt size. Numerical data is discrete if we count it in whole steps, such as siblings, and continuous if we measure it and it can take any value in a range, such as height. A phone number is categorical, because we never add two of them. The kind of data decides which average and which graph we can use.
This lesson is free to read. Enroll free to keep your place and take the tests.
Try the code and the simulations beside the lesson.
Look at a column of colours and a column of heights. You cannot add two colours, but you can add two heights. The kind of data tells you what you may do with it.
The quickest test for numerical data is to ask how you got the number. If you counted it, it is discrete. If you measured it, it is continuous.
You should find that the counted dot jumps from one whole number to the next. The measured dot can stop at 152.37 cm, or at any value between two marks.
The program lists the columns of the school table with the kind of each one.
| Data | Kind | Why |
|---|---|---|
| A phone number or a PIN code | categorical (nominal) | It is a label. Adding two makes no sense. |
| A roll number | categorical (nominal) | A label, not a quantity. |
| A rating from 1 to 5 stars | ordinal | It has an order, but the steps may not be equal. |
| Age in whole years | looks discrete | Age is really measured, but we round it to whole years. |
| The number of cars in a car park | discrete | Counted. |
| The time taken to run 100 m | continuous | Measured. |
A helpful test: can the average make sense? The average height of a class makes sense. The average colour, or the average phone number, does not.
Try each one on your own first. If you are stuck, open a hint. Then check with Show the answer.
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