For each problem, select the best response. (a) The owner of a chain of supermar
ID: 3060290 • Letter: F
Question
For each problem, select the best response.
(a) The owner of a chain of supermarkets notices that there is a positive correlation between the sales of beer and the sales of ice cream over the course of the previous year. Seasons when sales of beer were above average, sales of ice cream also tended to be above average. Likewise, during seasons when sales of beer were below average, sales of ice cream also tended to be below average. A plausible explanation of these facts is that
A. the sales records must be in error. There should be no association between beer and ice cream sales.
B. drinking beer causes a desire for ice cream or eating ice cream causes a thirst for beer.
C. a scatterplot of monthly ice cream sales versus monthly beer sales would show that a straight line describes the pattern in the plot, but it would have to be a horizontal line.
D. the sale of beer and ice cream may both be affected by another variable such as the outside temperature.
E. None of the above.
(b) A researcher observes that, on average, the number of divorces in cities with major league baseball teams is larger than in cities without major league baseball teams. The most plausible explanation for this observed association is
A. the high number of divorces is responsible for the presence of a major league baseball teams (more single men means potentially more fans at the ballpark, making it attractive for an owner to relocate to such cities).
B. the presence of a major league baseball team causes the number of divorces to rise (perhaps husbands are spending too much time at the ballpark).
C. the association is due to the presence of a confounding variable, namely the population of the city. (Major league teams tend to be in large cities with more people, hence a greater number of divorces.)
D. the observed association is purely coincidental. It is implausible to believe the observed association could be anything other than accidental.
E. None of the above.
(c) When possible, the best way to establish that an observed association is the result of a cause-and-effect relation is by means of
A. the least squares regression line.
B. the correlation coefficient.
C. a well designed experiment.
D. the square of the correlation coefficient.
E. None of the above.
Explanation / Answer
a) Option D. the sale of beer and ice cream may both be affected by another variable such as the outside temperature.
b) Option C. the association is due to the presence of a confounding variable, namely the population of the city. (Major league teams tend to be in large cities with more people, hence a greater number of divorces.)
c)Option A. the least squares regression line.
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