Logical reasoning PrepTest 151 · Section 2 · Question 12

Incorrect. This answer mentions the reliability of other brands, which doesn't affect an argument comparing the reliability of two specific brands. If you selected this answer because it suggests that KRV is such an outlier that maybe the study is off, then you made a very big jump that isn't supportable in an answer on the LSAT.

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Weaken

Stimulus Summary:
After controlling for market share, the Nerd Squad received a higher proportion of service requests for KRV computers than ProBit. Probit must be more reliable.

Answer Anticipation:
Even though the company controlled for market share, they didn't control for a possible sampling flaw. Whenever a study is done, check to see if the sample is representative. Here, there's no indication that the computers being brought to the company are a representative sample—maybe they advertise as specialists in fixing KRV machines. It'd be like Apple determining that their machines are unreliable because more people bring Macs than PCs to them to be fixed.

Also, as a side note, the conclusion specifically compares ProBit to KRV. There will probably be answers that mention the reliability of other machines, which will be out of scope.

Answer Explanation:
This answer raises the possibility that ProBit machines are sent to ProBit for servicing, and thus the sample at this independent service company is skewed away from it. Going back to our real-world example, since most Macs are serviced at the Mac store, independent companies would receive fewer requests to fix them, once controlling for market share, and would get a skewed view of their reliability.

Key Takeaway:
Whenever an argument references a study of any kind, dig into the sample to make sure it's representative. If you're not given a reason to believe it is (generally from the stimulus stating that it's representative, or it's large and random), then there's a good chance the answer will deal with that sampling flaw.

Incorrect. First, in Strengthen/Weaken questions, nonspecific comparisons ("more than") generally don't carry enough weight to affect the argument. One more than anyone else would qualify, but it probably wouldn't indicate a skewed sample. That said, even if the sample is skewed here, it's skewed in a direction that would help the conclusion. If more ProBit computers come to this service company than any other, and they still don't get nearly as high a proportion as KRV, ProBit is looking pretty good.

Incorrect. Since the stimulus states that market share was controlled for, this answer doesn't have an effect on the argument.

Incorrect. The amount of time a company has been in business doesn't necessarily reflect their quality.