Divide into groups of three or four students. Investigate the relationship between two variables by collecting your own paired sample data and using the methods of Section 13-6 to determine whether there is a correlation. Suggested topics:

• Is there a correlation between taste and cost of different brands of chocolate chip cookies (or colas)? (Taste can be measured on some number scale, such as 1 to 10.)
• Is there a correlation between salaries of professional baseball (or basketball or football) players and their season achievements (such as batting average or points scored)?
• Is there a correlation between car fuel consumption rates and car weights?
• Is there a correlation between the lengths of men’s (or women’s) feet and their heights?
• Is there a correlation between student grade-point averages and the amount of television watched?
• Is there a correlation between heights of fathers (or mothers) and heights of their first sons (or daughters)?

Rank Correlation From Section 13-6:

The rank correlation test (or Spearman’s rank correlation test) is a nonparametric test that uses ranks of sample data consisting of matched pairs. It is used to test for an association between two variables.