Lesson 2 Exploring Data with Graphs

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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?