Question
A certain laboratory is studying the incidence of fatal liver damage in rats. Sixty-five percent of all rats whose environments exposed them to low levels of the toxin sulfur dioxide died of liver disorder. Ninety percent of all rats who died of liver disorder, however, were not exposed to any environmental toxins.
Which of the following would provide a feasible explanation for the statistics above?
Which of the following would provide a feasible explanation for the statistics above?
Answer: Option D
:
D
Here's another study to ponder, and the stem alerts us to the fact that we need to find a plausible explanation for the statistics cited. The last sentence alone suggests that the stats are puzzling, or at least a bit unusual, which is reinforced by the contrast keyword however in the final sentence. So what's going on in this one? We have a significant number of rats dying of liver disorder after being exposed to sulfur dioxide, but most of the rats which died of liver disorder were not exposed to any environmental toxins. This is not unlike what we've seen previously: a situation in which what seems like the same groups are actually not. Specifically, you should have realized immediately that the 65% and the 90% figures refer to two different groups, and thus that there is no discrepancy in the statistics. The 65% figure represents all rats exposed to sulfur dioxide; 90% represents the percentage of all rats that died of liver disorder. (D) points this out. If only a small number of rats were exposed to sulfur dioxide, then it's not surprising that 90% of the rats that died of liver damage died of something other than sulfur dioxide exposure. After all, only a small number of them were exposed to sulfur dioxide in the first place. (D) wins.
The exclusively of causes of liver damage is irrelevant to this study. Any of the rats could have had both causes, but only one seriously enough to cause death.
(B) explains nothing. If there is only one cause of liver disease in rats, then what killed the rats that were not exposed?
As for this one, why did 65% of the exposed rats die, if environmental toxins are not very dangerous? This seems counterintuitive, and so it can't possibly help to explain the statistics.
(C)It's wrong for the same reason namely, that it contradicts the evidence. If 65% of the rats exposed to low levels of sulfur dioxide died, then most rats probably will suffer from such exposure.
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:
D
Here's another study to ponder, and the stem alerts us to the fact that we need to find a plausible explanation for the statistics cited. The last sentence alone suggests that the stats are puzzling, or at least a bit unusual, which is reinforced by the contrast keyword however in the final sentence. So what's going on in this one? We have a significant number of rats dying of liver disorder after being exposed to sulfur dioxide, but most of the rats which died of liver disorder were not exposed to any environmental toxins. This is not unlike what we've seen previously: a situation in which what seems like the same groups are actually not. Specifically, you should have realized immediately that the 65% and the 90% figures refer to two different groups, and thus that there is no discrepancy in the statistics. The 65% figure represents all rats exposed to sulfur dioxide; 90% represents the percentage of all rats that died of liver disorder. (D) points this out. If only a small number of rats were exposed to sulfur dioxide, then it's not surprising that 90% of the rats that died of liver damage died of something other than sulfur dioxide exposure. After all, only a small number of them were exposed to sulfur dioxide in the first place. (D) wins.
The exclusively of causes of liver damage is irrelevant to this study. Any of the rats could have had both causes, but only one seriously enough to cause death.
(B) explains nothing. If there is only one cause of liver disease in rats, then what killed the rats that were not exposed?
As for this one, why did 65% of the exposed rats die, if environmental toxins are not very dangerous? This seems counterintuitive, and so it can't possibly help to explain the statistics.
(C)It's wrong for the same reason namely, that it contradicts the evidence. If 65% of the rats exposed to low levels of sulfur dioxide died, then most rats probably will suffer from such exposure.
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