Stats Ch 7-9 Multiple Choice Practice

• -0.64

• -0.80

• 0.64

• 0.80

• There is insufficient information to answer this question.

Answer explanation

We are given r-squared = 0.64.

To find r, we square root 0.64 AND give it the same sign as the slope. So, r = -0.80

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CCSS.HSS.ID.C.8

CCSS.HSS.ID.B.6

A simple random sample of 25 world-ranked tennis players provides the following statistics:

Number of hours practiced per day: mean = 7.3, standard deviation = 1.2

Yearly winnings: mean = $1,820,000, standard deviation = $310,000

Correlation = 0.23

Based on this data, what is the LSRL that predicts winnings from number of hours practiced?

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CCSS.HSS.ID.C.8

CCSS.HSS.ID.B.6

CCSS.HSS.ID.C.7

• 0.23%

• 23%

• 7.29%

• 27%

• 52%

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CCSS.HSS.ID.C.8

CCSS.HSS.ID.C.7

• The model predicts that number of cancer deaths among Americans has been dropping by an average of 6,050 per year since 2001.

• The baseline number of cancer deaths among Americans is 550,000.

• The regression line explains 74.5% of the variation in cancer deaths among Americans over the years since 2001.

• The regression line explains 86.3% of the variation in cancer deaths among Americans over the years since 2001.

• Cancer will be cured in the year 2092.

Tags

CCSS.HSS.ID.C.7

• 0.28

• 0.45

• 0.56

• 0.90

• -0.28

Answer explanation

Correlation is unitless, so changing the values by shifting or rescaling or even switching x and y will not change the value of the correlation.

Tags

CCSS.HSS.ID.C.8

CCSS.HSS.ID.B.6

Which of the following are true statements about the correlation coefficient?

I. It is not affected by changes in the measurement units of the variables.

II. It is not affect by which variable is called x and which is called y.

III. It is not affected by extreme values.

• I and II

• I and III

• II and III

• I, II, and III

• I or II

Answer explanation

Correlation is unitless, so changing measurements or changing which variable is x and which is y will not change correlation.

Correlation is greatly affected by outliers.

Tags

CCSS.HSS.ID.C.8

CCSS.HSS.ID.B.6

• students who watch more TV tend to have lower SAT scores.

• the fewer hours in front of a TV, the higher a student's SAT scores.

• There is little relationship between weekly hours of television watched and SAT scores.

• there is a strong negative association between weekly hours of TV watched and SAT scores, but it would be wrong to conclude causation.

• A mistake in arithmetic was made.

Answer explanation

Correlation is never above 1 or below -1, so an r of -1.18 means a mistake was made in the calculations.

Tags

CCSS.HSS.ID.C.8

CCSS.HSS.ID.B.6

CCSS.HSS.ID.C.9

Which of the following statements about the correlation (r) are true?

I. When r = 0, there is no relationship between the variables.

II. When r = 0.20, 20% of the variables are closely related.

III. When r = 1, there is a perfect cause & effect relationship between the variables.

• I only

• II only

• III only

• I, II, and III

• All are false.

Answer explanation

None of the statements are true.

I. r = 0 means there's no linear relationship, not no relationship.

II. r is never measured as a percent.

III. correlation doesn't prove causation.

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CCSS.HSS.ID.C.8

CCSS.HSS.ID.B.6

CCSS.HSS.ID.C.9

Which of the following statements about residuals are true?

I. The mean of the residuals is always 0.

II. The regression line for a residual plot is a horizontal line.

III. The standard deviation of the residuals gives a measure of how the points in the scatterplot are spread around the regression line.

• I and II

• I and III

• II and III

• I, II, and III

• None are true.

Answer explanation

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CCSS.HSS.ID.B.6

CCSS.HSS.ID.A.3

A study is conducted relating AP Statistics exam scores to the total number of study hours for the AP Statistics class put in by students during the academic year, and the correlation is found to be 0.6. Which of the following are true statements?

I. On the average, a 40% increase in study time results in a 24% increase in exam scores.

II. 60% of a student's exam score can be explained by the number of study hours.

III. Higher exam scores tend to be associated with higher numbers of study hours.

• III only

• I and II

• I and III

• II and III

• I, II, and III

Tags

CCSS.HSS.ID.C.9

CCSS.HSS.IC.B.3