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A recent report determined that although only 3% of drivers on Maryland highways equipped their vechicles with radar detectors, 33% of all vechicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vechicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.
The conclusion drawn above depends on which of the following assumptions?
A. Drivers who equip their vechicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
B. Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
C. The number of vehicles that were ticketed for exceeding the speed limit were greater than the number of vehicles that were equipped with radar detectors.
D. Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the same period covered by the report.
E. Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report
Official answer: B
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My difficulity is that I know all A, C, D and E are impossible choices to be selected as an assumption. However, I also cannot convince myself to pick B as an answer because I really couldn't connect the evidence to conclusion by the assumption B. Would guys advise that my approach to crack is correct?
1st Evidence: 3% of all vehicles equipped with radar detector
2nd evidence: 33% of all ticketed vehicles for speeding equipped with radar detector
Conclusion: Drivers with radar detectors are more likely to exceed speed limit regularly than those who do not
Therefore, I need to make an assumption to connect 1st/2nd evidences so that the conclusion is valid to be drawn. So, my mind is the following figures:-
From 1st evidence: we have all 100 vehicles in town = 3 vehicles (3%) with radar detector + 97 without radar detectors
From 2nd evidence: let says we total have 3 vehicles were ticketed for speeding, then 1 vehicle (33%) with radar detector and 2 vehicles without detectors
Therefore, 1st & 2nd evdiences are meaning that only 1 out of 3 vehicles with radar detectors was ticketed for speeding.... I think up to this point, I cannot draw the conclusion as stated in the arguement because my analysis seems to go opposite direction from the conclusion. So now, I need to find a gap to assume something so that I can link up these 2 opposite things!!! OK, let even say B is the answer, which however can only show the drivers in regardless of with or without radar detector generally exceed speed limit if they used to exceed the speed limit. The assumption does NOT explictly point out those vehicles equipped with radars are regularly exceed the speed limit rather than those who do not, that however is the main point in the conlusion.
So, how to use "B" to link up the opposite direction between 1st/2nd evidences and conclusion?? Anyway "B" can not convince me to pick!! Please advise. | 
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发表于 2005-6-13 23:44:00
