PrepTest 114, Section 4, Question 5
Toxicologist: A survey of oil-refinery workers who work(45 more words not shown)
Each of the following, if(6 more words not shown)
- AMost oil-refinery workers(19 more words not shown)
- BHeadaches, fatigue, and(19 more words not shown)
- CSince the time(29 more words not shown)
- DRegions in which(29 more words not shown)
- EThe oil-refinery workers(27 more words not shown)
Reading the argument
What about refinery workers who don't work with MBTE? Do they have the same symptoms?
The complaints among exposed workers make MBTE worth investigating. But perhaps something else about refinery work accounts for the headaches, fatigue and shortness of breath. Gasoline more generally, or another exposure at work, could be responsible. We can't isolate this ingredient just by noting that these workers encountered it and reported symptoms.
The toxicologist then predicts more symptoms when gasoline containing MBTE becomes widely used. That requires the ingredient to be responsible for the problem and the concern to extend beyond this particular group of workers.
What we’re looking for
This is strengthen EXCEPT. Four answers will help the argument, and one won't. I'd first look for the comparison we were missing: fewer symptoms among otherwise relevant workers who don't work with MBTE. A clearer pattern or an explanation of how the ingredient produces the symptoms could also help. The supporting answers don't have to prove the entire causal claim.
Working the answers
- A
This supplies the comparison we wanted. Most refinery workers who don't work with MBTE lack the serious health problems involving these symptoms. That makes a problem with refinery work generally a less satisfying explanation than if the unexposed workers had the same troubling pattern.
Read the limits carefully: A says 'most,' and it concerns serious health problems. It doesn't say no unexposed worker ever has a headache. Still, the comparison adds support for focusing on MBTE, so A isn't the exception.
- BCorrect
The symptoms can accompany serious medical conditions. That might make them worrying, but it doesn't tell us whether MBTE causes them or whether wider use of MBTE will make them more common.
The missing link concerns the source and future incidence of the symptoms, not how serious a condition involving them might be. Learning that a headache can signal a serious problem doesn't identify this ingredient as its cause. B leaves the toxicologist's prediction unsupported in the relevant respect, making it the exception.
- C
The complaints increased in places after MBTE-containing gasoline was introduced. That gives us a further pattern connecting the change in fuel with the symptoms, this time outside the refinery-worker survey. Other things could have changed too, so it isn't proof. But the timing and broader setting add support to the predicted increase as use spreads.
- D
This compares similar regions that differ in the kind of gasoline they use. The regions using MBTE have much more of the symptoms than the regions using MBTE-free gasoline. That connects the ingredient to the outcome through a relevant comparison, strengthening the argument. We needn't assume the regions are identical in every conceivable way to recognize the added support.
- E
This helps with extending the survey to the broader population. The selected workers weren't an unusual group in their prior medical histories or other relevant respects. That reduces a concern that the troubling result reflects an especially susceptible sample whose experience tells us little about everyone else.
Representativeness doesn't prove that MBTE caused the symptoms; another workplace exposure could still matter. E nevertheless makes the survey more relevant to the wider prediction, which is enough for a strengthener.
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