PrepTest 114

Incorrect. This answer establishes a control group—oil workers who lack the supposed cause and don't have the effect. This strengthens the argument, so we can eliminate this answer.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Bizarro Strengthen

Stimulus Summary:
Survey - Oil workers who work with MBTE have some bad symptoms
Conclusion - When oil containing MBTE is more widely used, we'll see an increase of those symptoms

Answer Anticipation:
Since this is a Bizarro Strengthen question, we can expect there to be several ways to strengthen the argument! So it's a good thing that there are a couple features of this argument that suggest specific flaws.

First, the argument is based on a survey, and whenever there's a survey, we should think about a Sampling flaw, and a Correlation/Causation flaw.

Let's start with the Sampling flaw. The sample here is oil workers who work with MBTE. The conclusion, however, is about all people exposed to MBTE through gasoline. It's possible that oil workers and their exposure isn't representative of the general population being exposed via gasoline. Maybe the oil workers are exposed to higher concentrations of the stuff, or they're exposed in liquid form, and MBTE completely burns up in gasoline. Maybe pure MBTE is dangerous, but MBTE mixed into gasoline isn't! Any answer that makes the oil workers and their exposure representative of the general public being exposed to MBTE through gasoline will strengthen this argument.

Second, a Correlation/Causation flaw. The conclusion is that we should "expect" an increase in certain symptoms based on the use of MBTE—that's not causal itself, but it's relying on a causal assumption. Since the survey results are based on a correlation between people who work with MBTE and these symptoms, there is a Correlation/Causation flaw present, and we can strengthen the argument using the regular answer choice types:
(1) Eliminate an alternative cause
(2) Find more examples of cause and effect going together (e.g., another occupation that has exposure to MBTE also has workers with the same symptoms)
(3) A control group (oil workers who work somewhere that doesn't use MBTE don't have the symptoms)

Answer Explanation:
The argument is over the causes of these symptoms, not how serious they are, so this answer has no effect on the argument. If you thought this established an alternative cause ("several medical conditions"), there are two issues with that. First, those medical conditions could be related to chemical exposure, and so they may not be separate from MBTE-related symptoms! Second, if these medical conditions are considered alternative causes, then they would weaken the argument since they would provide an alternative explanation to the symptoms.

Key Takeaway:
Bizarro Strengthen questions are going to have 4 answers that strengthen the argument, so there are frequently multiple flaws in the argument. Be sure to consider any that are hinted at by the details!

Incorrect. This answer establishes more examples of the supposed cause and effect going together, so this answer strengthens the argument.

Incorrect. This answer not only establishes more examples of the supposed cause and effect going together, but by establishing that the regions in question are similar to ones that lack the cause and see a decreased incidence of the effect, it also brings up a control group.

Incorrect. This answer goes out of its way to establish that the sample was very representative, thus strengthening the argument.