Categorical Data
Types of Variables
Categorical
Quantitative
Discrete
Continuous
Categorical Variables
Values that are category names or group variables
Show frequencies or relative frequencies that observations fall into each category
Quantitative
Numerical values for a measured or counted quantity
Can be used for mathematical operations
Categorical data can be in numbers
Numerical data can be in categories
Discrete Variable
A countable number of values
Continuous Variable
Can take on infinitely many values
Discrete values can be treated as continuous if there are a lot of those values
Graphs for Categorical Data
Pie (circle) charts- categories in relation to a whole
Bar graphs/charts- categories in relation to each other
Side-by-side bar graphs- bars are grouped together and placed side by side
Segmented bar graphs- displays variable distribution as segments in a rectangle
Mosiac plots- a three-way split of data structured like a segmented bar graph
Two-way Table
Two categorical variables can be summarized in a two-way table
Gives counts of observations for each combination of variables
Joint Relative Frequency
Each cells percentage of the total (in a table)
Marginal Relative Frequency
Focuses on only one categorical variable
Row and column totals for a two-way table
Conditional Relative Frequency
Relative frequency for specific row or column
Assosiation
When one variable helps to predict the other
Categorical Data
Types of Variables
Categorical
Quantitative
Discrete
Continuous
Categorical Variables
Values that are category names or group variables
Show frequencies or relative frequencies that observations fall into each category
Quantitative
Numerical values for a measured or counted quantity
Can be used for mathematical operations
Categorical data can be in numbers
Numerical data can be in categories
Discrete Variable
A countable number of values
Continuous Variable
Can take on infinitely many values
Discrete values can be treated as continuous if there are a lot of those values
Graphs for Categorical Data
Pie (circle) charts- categories in relation to a whole
Bar graphs/charts- categories in relation to each other
Side-by-side bar graphs- bars are grouped together and placed side by side
Segmented bar graphs- displays variable distribution as segments in a rectangle
Mosiac plots- a three-way split of data structured like a segmented bar graph
Two-way Table
Two categorical variables can be summarized in a two-way table
Gives counts of observations for each combination of variables
Joint Relative Frequency
Each cells percentage of the total (in a table)
Marginal Relative Frequency
Focuses on only one categorical variable
Row and column totals for a two-way table
Conditional Relative Frequency
Relative frequency for specific row or column
Assosiation
When one variable helps to predict the other