# Different Types Of Data

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Chapter 2
Data
Chapter 2 – Slide 1

Ch.2: Data
Learning Objectives
1)Identify the context of your data
2)Distinguish different types of data

Chapter 2 – Slide 2

2.1 What Are Data?
• Data values or observations are information collected regarding some subject
• Data can be numbers, names, etc., and tell us the “Who and What”
• Data are useless without their context
• Data are often organized into a data table like that below

Chapter 2 – Slide 3

2.1 What Are Data?
The rows of a data table correspond to individual cases about Whom (or about Which – if they are not people) we record some characteristics
These characteristics may be collected on or about …
• respondents – individuals who answer a survey
• subjects or participants – people in an experiment
• experimental units – animals, plants, websites, or other inanimate objects

Cases ⎨

Chapter 2 – Slide 4

2.1 What Are Data?
The characteristics recorded about each individual or case are called variables
These are usually shown as the columns of a data table and identify What has been measured

6 4 4 4 4 4 4 4 4 Variables
44 7 4 4 4 4 4 4 4 4 4 48

Chapter 2 – Slide 5

2.1 What Are Data?
Data tables are cumbersome for complex data sets, so often two or more separate data tables are linked together in a relational database
Each data table included in the database is a relation because it is about a specific set of cases with information about each of these cases for all of the variables

Chapter 2 – Slide 6

2.1 What Are Data?
Example: A typical relational database is provided consisting of three relations: customer data, item data, and transaction data
For example, we can look up a customer to see what items they purchased, or we may look up an item to see who purchased it

Chapter 2 – Slide 7

2.2 Variable Types
When a variable names categories and answers questions about how cases fall into those categories, it is called a categorical variable - you may see them called qualitative variable When a variable has measured numerical values with units and the variable tells us about the quantity of what is measured, it is called a quantitative variable

Chapter 2 – Slide 8

2.2 Variable Types
Categorical variables …
• arise from descriptive responses to questions like
“What kind of advertising do you use?” or “Do you invest in stock market?”
• may only have two possible values (like “Yes” or “No”)
• may be a number like a telephone area code

Chapter 2 – Slide 9

2.2 Variable Types
Some quantitative variables have units. The units indicate …
• how each value has been measured
• the corresponding scale of measurement
• how much of something we have
• how far apart two values are
Other quantitative variables have no units, such as …
• Number of visits to a web site
• Number of shares of a company traded in Toronto
Stock Exchange
Chapter 2 – Slide 10

2.2 Variable Types
Some variables can be both categorical and quantitative
How data are classified depends on Why we are collecting the data
For example, variable Age is obviously the quantitative value, measured in years, that may be used for finding the average age of customers
Age categories such as Child, Teen, Adult can be the categorical value used to classify books for an internet store