Lesson 2 Exploring Data with Graphs

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Lesson 2 Exploring Data with Graphs Learn …. The Different Types of Data The Use of Graphs to Describe Data Section 2.1 What are the Types of Data? In Every Statistical Study: Questions are posed Characteristics are observed Characteristics are Variables

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Lesson 2Exploring Data with Graphs
• Learn ….

The Different Types of Data

The Use of Graphs to Describe

Data

Section 2.1

What are the Types of Data?

In Every Statistical Study:
• Questions are posed
• Characteristics are observed
Characteristics are Variables

A Variable is any characteristic that is recorded for subjects in the study

Variation in Data
• The terminology variablehighlights the fact that data values vary.
Example: Students in a Statistics Class
• Variables:
• Age
• GPA
• Major
• Smoking Status
Data values are called observations
• Each observation can be:
• Quantitative
• Categorical
Categorical Variable
• Each observation belongs to one of a set of categories
• Examples:
• Gender (Male or Female)
• Religious Affiliation (Catholic, Jewish, …)
• Place of residence (Apt, Condo, …)
• Belief in Life After Death (Yes or No)
Quantitative Variable
• Observations take numerical values
• Examples:
• Age
• Number of siblings
• Annual Income
• Number of years of education completed
Graphs and Numerical Summaries
• Describe the main features of a variable
• For Quantitative variables: key features are center and spread
• For Categorical variables: key feature is the percentage in each of the categories
Quantitative Variables
• Discrete Quantitative Variables

and

• Continuous Quantitative Variables
Discrete
• A quantitative variable is discrete if its possible values form a set of separate numbers such as 0, 1, 2, 3, …
Examples of discrete variables
• Number of pets in a household
• Number of children in a family
• Number of foreign languages spoken
Continuous
• A quantitative variable is continuous if its possible values form an interval
Examples of Continuous Variables
• Height
• Weight
• Age
• Amount of time it takes to complete an assignment
Frequency Table
• A method of organizing data
• Lists all possible values for a variable along with the number of observations for each value
Example: Shark Attacks

Example: Shark Attacks

• What is the variable?
• Is it categorical or quantitative?
• How is the proportion for Florida calculated?
• How is the % for Florida calculated?

Example: Shark Attacks

• Insights – what the data tells us about shark attacks
Identify the following variable as categorical or quantitative:

Choice of diet

(vegetarian or non-vegetarian):

• Categorical
• Quantitative

Identify the following variable as categorical or quantitative:

Number of people you have known who have been elected to political office:

• Categorical
• Quantitative
Identify the following variable as discrete or continuous:

The number of people in line at a box office to purchase theater tickets:

• Continuous
• Discrete
Section 2.2

How Can We Describe Data Using Graphical Summaries?

Graphs for Categorical Data
• Pie Chart: A circle having a “slice of pie” for each category
• Bar Graph: A graph that displays a vertical bar for each category
Pie Chart vs. Bar Chart
• Which graph do you prefer?
• Why?