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# Lesson 2 - PowerPoint PPT Presentation

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

What are the Types of Data?

• Questions are posed

• Characteristics are observed

Characteristics are Variables

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

• The terminology variablehighlights the fact that data values vary.

• Variables:

• Age

• GPA

• Major

• Smoking Status

Data values are called observations

• Each observation can be:

• Quantitative

• Categorical

• 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)

• Observations take numerical values

• Examples:

• Age

• Number of siblings

• Annual Income

• Number of years of education completed

• 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

• Discrete Quantitative Variables

and

• Continuous Quantitative Variables

• A quantitative variable is discrete if its possible values form a set of separate numbers such as 0, 1, 2, 3, …

• Number of pets in a household

• Number of children in a family

• Number of foreign languages spoken

• A quantitative variable is continuous if its possible values form an interval

• Height

• Weight

• Age

• Amount of time it takes to complete an assignment

• A method of organizing data

• Lists all possible values for a variable along with the number of observations for each value

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?

• 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

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

• Continuous

• Discrete

The weight of a dog:

• Continuous

• Discrete

Section 2.2 quantitative:

How Can We Describe Data Using Graphical Summaries?

Graphs for Categorical Data quantitative:

• 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 quantitative:

Bar Chart quantitative:

Pie Chart vs. Bar Chart quantitative:

• Which graph do you prefer?

• Why?