Lesson 9
Looking for Associations
Problem 1
A scientist wants to know if the color of the water affects how much animals drink. The average amount of water each animal drinks was recorded in milliliters for a week and then graphed. Is there evidence to suggest an association between water color and animal?
cat intake (ml) | dog intake (ml) | total (ml) | |
---|---|---|---|
blue water | 210 | 1200 | 1410 |
green water | 200 | 1100 | 1300 |
total | 410 | 2300 | 2710 |
![Bar graph with two pairs of bars.](https://cms-im.s3.amazonaws.com/Dp7qnk3dCGmGxGWbYpxpRQ6Q?response-content-disposition=inline%3B%20filename%3D%228-8.6.PP.C.Image.02.png%22%3B%20filename%2A%3DUTF-8%27%278-8.6.PP.C.Image.02.png&response-content-type=image%2Fpng&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAXQCCIHWF3XOEFOW4%2F20240630%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20240630T192228Z&X-Amz-Expires=604800&X-Amz-SignedHeaders=host&X-Amz-Signature=5f8bda668b56245436e765061bca217661eed7c4a4df90acc8da04782528cdb9)
Solution
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Problem 2
A farmer brings his produce to the farmer’s market and records whether people buy lettuce, apples, both, or something else.
bought apples | did not buy apples | |
---|---|---|
bought lettuce | 14 | 58 |
did not buy lettuce | 8 | 29 |
Make a table that shows the relative frequencies for each row. Use this table to decide if there is an association between buying lettuce and buying apples.
Solution
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Problem 3
Researchers at a media company want to study news-reading habits among different age groups. They tracked print and online subscription data and made a 2-way table.
internet media | print media | |
---|---|---|
18-25 year olds | 151 | 28 |
26-45 year olds | 132 | 72 |
46-65 year olds | 48 | 165 |
- Create a segmented bar graph using one bar for each row of the table.
- Is there an association between age groups and the method they use to read articles? Explain your reasoning.
Solution
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Problem 4
Using the data in the scatter plot, what is a reasonable slope of a model that fits this data?
![A scatterplot. Horizontal, from 0 to 28, by 4’s. Vertical, from 1960 to 2010, by 10’s. 19 data points trend linearly upward and right.](https://cms-im.s3.amazonaws.com/8snMRqxUhji8FB3qnJy7KQFU?response-content-disposition=inline%3B%20filename%3D%228-8.6.PP.B.Image.30.png%22%3B%20filename%2A%3DUTF-8%27%278-8.6.PP.B.Image.30.png&response-content-type=image%2Fpng&X-Amz-Algorithm=AWS4-HMAC-SHA256&X-Amz-Credential=AKIAXQCCIHWF3XOEFOW4%2F20240630%2Fus-east-1%2Fs3%2Faws4_request&X-Amz-Date=20240630T192228Z&X-Amz-Expires=604800&X-Amz-SignedHeaders=host&X-Amz-Signature=dcac5aa5690a18527d2192b069a44c5c867fcc10590103bb5c4317783cde3067)
-2.5
-1
1
2.5
Solution
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(From Unit 6, Lesson 6.)