Chapter 1 Notes: Picturing Distributions with Graphs

Individuals: Objects described by a set of data (people, animals, things).
- Example: In the fuel economy dataset, individuals are car makes and models like Subaru Impreza.
Variable: Characteristic of an individual that can take different values.
- Example: Vehicle Class, Transmission Type, Number of Cylinders, City mpg, Highway mpg, and Annual Fuel Cost.
Categorical Variable: Places individuals into groups or categories.
- Example: Vehicle Class and Transmission Type.
Quantitative Variable: Takes numerical values where arithmetic operations make sense, usually recorded with a unit of measurement.
- Example: Number of Cylinders, City mpg, Highway mpg, and Annual Fuel Cost.

Distribution: Tells us what values a variable takes and how often it takes those values.
For categorical variables, the distribution lists categories and the count or percentage of individuals in each category.
Distributions can be displayed using:
- Bar Graph: Represents each category as a bar.
- Steps to create a bar graph in excel are:
  - Enter the distribution data into an excel spreadsheet.
  - Highlight the distribution data.
  - Click insert.
  - Click recommended charts and select bar graph.
  - Click Ok.
- Pie Chart: Shows the distribution of a categorical variable as slices of a pie.
- Steps to create a pie chart in excel are:
  - Enter the distribution data into an excel spreadsheet.
  - Highlight the distribution data.
  - Click insert.
  - Click recommended charts and select pie chart.
  - Click Ok.
- Pie charts must include all categories that make up a whole.