Lesson 9

Looking for Associations

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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.

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
  1. Create a segmented bar graph using one bar for each row of the table.
  2. 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.
A:

-2.5

B:

-1

C:

1

D:

2.5

Solution

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(From Unit 6, Lesson 6.)