# Lesson 2 Exploring Data with Graphs - PowerPoint PPT Presentation

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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 2 Exploring Data with Graphs

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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

### Identify the following variable as discrete or continuous:

The weight of a dog:

• 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?