Algebra 1 / Unit 10: Data and Statistics
10.3 Two-Way Tables
Notes
A two-way table shows counts for two categorical variables.
- Joint frequency: a count in the body of the table.
- Marginal frequency: a row or column total.
- Conditional relative frequency: a count divided by its row (or column) total, like the fraction of 9th graders who prefer soccer.
- If conditional frequencies differ a lot between groups, the variables may be associated.
Practice
Of 80 students, 30 play an instrument; 18 of those also play a sport. What fraction of instrument players play a sport?
$\displaystyle \frac{18}{30} = \frac{3}{5}$.
In a two-way table, the total of a row is called a:
Totals are in the margins.
60% of seniors and 58% of juniors say they prefer online homework. This suggests:
The conditional percents are almost the same.
Ready for more? Take the Unit 10 test.