Overview
This lecture explains how to organize and summarize categorical data using a two-way table, which displays relationships between two categorical variables.
Categorical Data
- Categorical data uses words to describe variables, like eye color (blue, green) or yes/no responses.
- Such data must be consolidated for analysis since responses are in word form.
Collecting and Summarizing Responses
- Gather how many times each categorical response occurs (frequency) before making any tables.
- Example: Survey questions about gender (man/not a man) and seat belt use (always/not always).
- Coding yes/no as '1' and '0' helps with data entry and analysis.
Two-Way Tables
- A two-way table records frequencies for combinations of two categorical variables.
- Columns and rows represent different variables, and each cell counts how many people fit that combination.
- Row and column totals summarize the frequency for each individual variable.
- The table format allows for quick identification of relationships and summary statistics.
Key Terms & Definitions
- Categorical data — Variables described with words (e.g., eye color, yes/no).
- Frequency — The count of times a specific response occurs in data collection.
- Two-way table — A table that summarizes the relationship between two categorical variables by organizing their frequencies.
Action Items / Next Steps
- Practice constructing a two-way table using sample categorical data.
- Review the process of coding yes/no variables for easier analysis.