Classifying Data

Video coming soon3 worked examples

Theory

Before analysing any data, it is crucial to understand exactly what type of data you are working with, as this determines which statistical tests and diagrams are appropriate to use.

Data can be broadly split into two main groups: Numerical (number-based) and Categorical (word or group-based). These are then broken down further into four specific classifications:

1. Numerical Data (Quantitative)

Data that represents quantities or measurements.

Numerical Discrete: Data that can only take specific, exact values. This is usually data that is counted (e.g., number of siblings, number of cars).
Numerical Continuous: Data that can take any value within a specific range. This is usually data that is measured (e.g., height, weight, time).

2. Categorical Data (Qualitative)

Data that is grouped into descriptive categories.

Categorical Nominal: Data divided into descriptive categories that have no natural order or ranking (e.g., eye colour, car brand, favourite fruit).
Categorical Ordinal: Data divided into categories that have a logical, natural order or ranking (e.g., clothing sizes [Small, Medium, Large], or satisfaction ratings [Poor, Good, Excellent]).

Worked examples

Example 1

Example 1: The Smartphone Survey

A tech company is surveying people about their smartphones. Decide which of the four data classifications best describes each piece of information collected:

(a) The brand of the smartphone (e.g., Apple, Samsung, Google).
(b) The number of apps installed on the device.
(c) The battery life of the phone in hours.
(d) The condition of the phone (Poor, Fair, Good, Excellent).

(a) Categorical Nominal (They are word-based categories with no natural ranking).
(b) Numerical Discrete (You can count the exact number of apps; you cannot have 12.4 apps).
(c) Numerical Continuous (Time is a measurement that can take any value, e.g., 14.258 hours).
(d) Categorical Ordinal (Word-based categories that have a natural, logical ranking).

Example 2

Example 2: The Coffee Shop

A local coffee shop tracks data on its daily sales. Classify each of the following variables:

(a) The temperature of the milk used in each coffee.
(b) The size of the drink ordered (Small, Regular, Large).
(c) The type of milk requested (Oat, Soya, Dairy, Almond).
(d) The number of customers served each hour.

(a) Numerical Continuous (Temperature is a measurement).
(b) Categorical Ordinal (Categories with a distinct size order).
(c) Categorical Nominal (Categories with no natural order).
(d) Numerical Discrete (Counted whole numbers).

Example 3

Example 3: Animal Rescue Centre

An animal rescue centre updates the profiles of the dogs in its care. Identify the data type for each of the following:

(a) The breed of the dog.
(b) The weight of the dog in kilograms.
(c) The aggression level of the dog (Low, Medium, High).
(d) The number of previous owners the dog has had.

(a) Categorical Nominal
(b) Numerical Continuous
(c) Categorical Ordinal
(d) Numerical Discrete

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8 Classifying Data questions with answers and video solutions