Logical reasoning PrepTest 141 · Section 4 · Question 10

Incorrect. Even if the Super XL left dirt in the carpet, that dirt was also left by the first vacuum and the Super XL picked up dirt the first vacuum missed.

Incorrect. The comparison is between the Super XL and this old vacuum, not the model of vacuum. As such, the Super XL's performance as it ages is out of scope.

Incorrect. The argument's conclusion is just that the Super XL is the "better" vacuum, not the best, so this answer is out of scope.

Incorrect. The test was designed to show that the Super XL picked up dirt that was missed by the old vacuum. Even if the first vacuum picked up more dirt, that dirt then would have been impossible for the Super XL to remove, so this comparison is out of scope.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Errors in Reasoning

Stimulus Summary:
Test: An old vacuum was used, and then the Super XL went over the same spot, picking up dirt left behind by the first vacuum.
Conclusion: The Super XL is the better vacuum!

Answer Anticipation:
In order to compare two items, you have to run the same test on them. Here, the "picks up what the other left behind" test is only run on the Super XL. It's possible that, had the Super XL been used first, the same pattern of dirt being left behind and picked up by the other vacuum would have been seen. The correct answer should highlight that the test's comparison between the two vacuums was incomplete in this way.

Answer Explanation:
This answer highlights that the comparison between the vacuums wasn't fair. It's possible that all vacuums leave some dirt behind, and so the Super XL picking up some dirt that the first vacuum missed doesn't prove it's better. The test would have to be run in both orders (Super XL → Old vacuum as well as Old Vacuum → Super XL) to see which one was better.

Key Takeaway:
When two items are being compared, they have to be compared over the same relevant metrics. Here, the two vacuums were not both run through the same test, so any conclusion about one being better than the other was flawed.