Data Management

Lesson

**Numerical** data is **quantitative** and **can be counted, ordered** and **measured**.

**Numerical** data can be split into two categories: **continuous** and **discrete**.

A data set is said to be continuous if the observed values may take on **any value** within a finite or infinite interval.

Height, weight, temperature, the time taken to run $100$100 metres.

Do you notice how all these examples could be anywhere on a scale interval and could even be fractions? For example, it might be $25.3$25.3 degrees or a man might be $182.13$182.13cm tall.

A data set is said to be discrete if the numerical values can be **counted** but are **distinct** and **separate** from each other. They are often (but not always) whole number values.

The number of goal scored in a game, the number of people in a class, the number of pets people have.

Do you notice how all these examples have distinct values? For example, you couldn't score $2.5$2.5 goals in a game of soccer or own $\frac{1}{4}$14 of a dog so there is no continuity between the scores.

However, in some tournaments, half a point is awarded for a draw. In this case, there could be a score of $2.5$2.5, but there still could not be a score of $2.25$2.25 or $2.75$2.75 so the data is still discrete.

**Categorical** data is non-numerical. In other words, it describes the **qualities** or **characteristics** of a data set. It is also called qualitative data.

There are two types of categorical data: **ordinal** and **nominal**.

A set of data is said to be ordinal if the values **can be counted and ordered but not measured**.

Rating scales are examples of ordinal data. The finishing places in a race are another example of ordinal data. Think about it- the positions in a race can be ordered or ranked. Finishing first means you were faster than the person who came second and the person who finished eighth was slower than the person who finished sixth. However, the differences between the finishing times may not be the same between all competitors. Check out the picture below. The times between first and second will be really close- maybe less than half a second. However, the time between second and third may be more than a second. There is not a fixed interval.

*Nominal* basically means *name*. In other words, data is split up based on different names or characteristics. Nominal data may be the names of countries you have visited or your favourite colours. We could assign these different characteristics a number where the numbers are simply labels. In other words, you are giving numerical data numerical labels. You **can count but not order or measure** nominal data.

We could divide a group of people into males and females. We could also use "male" and "female" as our two categories to count how many men and women there were in the group.

Which of the following are examples of numerical data? (Select all that apply)

favourite flavours

Amaximum temperature

Bdaily temperature

Ctypes of horses

D

Which one of the following data types is discrete?

The number of classrooms in your school

ADaily humidity

BThe ages of a group of people

CThe time taken to run $200$200 metres

D

Classify this data into its correct category:

Weights of dogs

Categorical Nominal

ACategorical Ordinal

BNumerical Discrete

CNumerical Continuous

D

Distinguish between discrete data and continuous data