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are good guidelines, they should not be treated as a rule. Context is also important when determining whether to call a relationship strong or weak.
Here are some questions for discussion.
• “How would you describe the relationship between distance and time for Priya’s trips? Explain your reasoning.” (It is a strong positive relationship. It is strong because and it is positive because time, , tends to increase as distance, , increases.)
• Refer students to scatter plot D from the warm-up. “How would you describe the relationship between wait time and customer satisfaction? The correlation coe cient is .” (It is a negative relationship. It is a moderately strong relationship, since there are many other factors that might a ect satisfaction.)
• “What is an example of data with a strong, negative relationship?” (An example of a strong negative relationship could be between the time it takes you to run a mile and your speed. As your speed increases, the time decreases.)
8.3 Correlation Zoo
10 minutes
The mathematical purpose of this activity is to use the correlation coe cient to describe the relationship between two variables.
Launch
Arrange students in groups of 2. Give students an example of the type of response expected by telling students, “The cost of a package of lightbulbs and the number of lightbulbs in the package has a correlation coe cient value near 1. This means that these variables have a very strong, positive relationship. In other words, the price of the package is very closely related to the number
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Teacher Guide Algebra