SAT OwlQuestion bank / Evaluating statistical claims: observational studies and experiments
Last year, City P reported bicycle thefts and City Q reported bicycle thefts. A news article concluded that a bicycle in City P is more likely to be stolen than a bicycle in City Q. Which of the following additional pieces of information would be most useful for evaluating this conclusion?
The number of bicycles in each city
The number of bicycle thefts in each city the year before
The average price of a bicycle in each city
The number of police officers in each city
Show answer and explanation
Answer: A
How likely a bicycle is to be stolen depends on the theft rate, the number of thefts divided by the number of bicycles. If City P has many more bicycles than City Q, its rate could be lower even though it had more thefts. So the number of bicycles in each city is needed.
Choice B adds more theft counts, but counts from another year still don't show how many bicycles could have been stolen.
Why the other choices are wrong
- B. Counts from another year still don't show how many bicycles could have been stolen.
- C. Bicycle prices don't tell you the chance that a given bicycle is stolen.
- D. The number of police officers doesn't tell you the theft rate per bicycle.
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