Unit 2 Review

It is estimated that 56% of Americans have pets. However, favorite pet of choice differs by geographic location. A random sample of pet owners is cross-classified by geographic location and pet of choice. The results are summarized in the following segmented bar chart.

Which of the following is an incorrect conclusion?

• More pet owners in the South than the North answered "Other".

• Twice as many pet owners in the North answered "Dogs" than answered "Other".

• The same number of pet owners in the South answered "Cats" as answered "Other".

• In both the North and South, the same proportion of pet owners answered "Dogs".

• A greater proportion of pet owners in the North than in the South answered "Cats".

Answer explanation

We are able to compare amounts/percentages within a specific bar. We are able to compare the percentages between bars.

We know nothing about the overall counts or the counts for North vs South. Therefore, we cannot compare the amounts between the bars.

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CCSS.8.SP.A.4

Two hundred fifty randomly chosen people raised in the U.S. were asked their expression for "soft drink" and the geographic region where they were raised. The results are summarized in the two-way table.

What was the marginal frequency of "Coke"?

• 10

• 5

• 20

• 50

• 40

Answer explanation

Question 2 asked for the marginal frequency of “Coke” – This is just the count of people in the “Coke” row, which is 50 (10 + 5 + 5 + 30).

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CCSS.8.SP.A.4

Two hundred fifty randomly chosen people raised in the U.S. were asked their expression for "soft drink" and the geographic region where they were raised. The results are summarized in the two-way table.

What was the marginal frequency of "Midwest"?

• 70

• 5

• 20

• 50

• 75

Answer explanation

Question 3 asked for the marginal frequency of “Midwest” – This is just the count of people in the “Midwest” column, which is 75 (5 + 20 + 50).

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CCSS.8.SP.A.4

Two hundred fifty randomly chosen people raised in the U.S. were asked their expression for "soft drink" and the geographic region where they were raised. The results are summarized in the two-way table.

What was the joint frequency of "Pop" and "Northeast"?

• 10

• 50

• 20

• 5

• 75

Answer explanation

Question 4 asked for the joint frequency of “Pop” and “Northeast” – This is just the count of people in the intersection of the “Pop” row and the “Northeast” column, which is 20.

Tags

CCSS.8.SP.A.4

Two hundred fifty randomly chosen people raised in the U.S. were asked their expression for "soft drink" and the geographic region where they were raised. The results are summarized in the two-way table.

What was the relative frequency of "Soda" and "West"?

• 16%

• 20%

• 46%

• 22%

• 68%

Answer explanation

Question 5 asked for the joint relative frequency of “Soda” and “West” – This is the ratio of the joint frequency of “Soda” and “West” to sample size.  The joint frequency of "Soda” and “West” is 40, while the sample size is 250.  Thus, the ratio is 40/250 = 16%.

Tags

CCSS.8.SP.A.4

Two hundred fifty randomly chosen people raised in the U.S. were asked their expression for "soft drink" and the geographic region where they were raised. The results are summarized in the two-way table.

What was the marginal relative frequency of "South"?

• 12%

• 16%

• 2%

• 40%

• 32%

Answer explanation

Question 6 asked for the marginal relative frequency of “South” – This is the ratio of total “South” to sample size.  The marginal frequency of "South" is 40 (30 + 5 + 5), while the sample size is 250.  Thus, the ratio is 40/250 = 16%.

Tags

CCSS.8.SP.A.4

Two hundred fifty randomly chosen people raised in the U.S. were asked their expression for "soft drink" and the geographic region where they were raised. The results are summarized in the two-way table.

What was the marginal relative frequency of "Pop"?

• 8%

• 20%

• 32%

• 34%

• 40%

Answer explanation

Question 7 asked for the marginal relative frequency of “Pop” – This is the ration of total “Pop” to sample size.  The marginal frequency of “Pop” is 85 (20 + 50 + 10 + 5), while the sample size is 250.  Thus, the ratio is 85/250 = 34%

Tags

CCSS.8.SP.A.4

Two hundred fifty randomly chosen people raised in the U.S. were asked their expression for "soft drink" and the geographic region where they were raised. The results are summarized in the two-way table.

What was the conditional relative frequency of Midwesterners that call it "Soda"?

• 75%

• 20%

• 27%

• 17%

• 40%

Answer explanation

Question 8 asked for the conditional relative frequency of Midwesterners that call it "Soda".  This first restricts us to looking at just the column for “Midwest”.  In the “Midwest” column there were a total of 75 people, and 20 people in the Midwest call it “Soda”.  Thus, the ratio is 20/75 = 27%.

Tags

CCSS.8.SP.A.4

Two hundred fifty randomly chosen people raised in the U.S. were asked their expression for "soft drink" and the geographic region where they were raised. The results are summarized in the two-way table.

What was the conditional relative frequency of someone calling it "Coke" being from the South?

• 60%

• 12%

• 15%

• 75%

• 65%

Answer explanation

Question 9 asked for the conditional relative frequency of someone calling it "Coke" being from the South?  This first restricts us to looking at just the “Coke” row.  In the “Coke” row there were a total of 50 people, and 30 people that call it Coke were from the South.  Thus, the ratio is 30/50 = 60%.

Tags

CCSS.8.SP.A.4

When asked to choose their favorite hip-hop artist, 8 students chose Eminem, 5 picked 2Pac, 6 picked Notorious B.I.G., 3 picked Nas, and 3 picked Jay-Z.

Among those students who did not choose Eminem, what proportion chose Jay-Z?

• 12%

• 18%

• 20%

• 32%

• 26%

Answer explanation

This question is look at students who did not choose Eminem. So we completely disregard the first bar and only add up the bars for Tupac, B.I.G, Nas, and Jay-Z (which total 17). Out of this group, we want to look at those that prefer Jay-Z (only 3 students). Therefore, the ratio would be 3/17 = 18%

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CCSS.8.SP.A.4