PrepTest 153

Incorrect. Totally different reasoning; this is about "over" versus "exactly at," which wasn't an issue in the stimulus.

Incorrect. This answer choice expresses a part-to-whole fallacy, rather than misuse of logical force.

Incorrect. This is a probability issue and does involve logical force, but rather than trying to support a moderate conclusion with a single weak premise, it improperly derives certainty from a possibility. It's also a sampling fallacy (deriving a certain conclusion about humans from a study on rats).

Incorrect. This is an issue of causality more than logical force. Something that can contribute to success is not necessarily the exclusive cause of success. Doesn't match the anticipation of "weak premise, moderate conclusion."

Correct. Argument or Facts:
Argument

Valid or Flawed:
Flawed

Question Type:
Flawed Parallel Reasoning

Stimulus Summary:
IF daily doses of Vitamin C, THEN chance of getting a cold decreases somewhat. So, IF you get a cold, THEN you probably didn't take daily doses of Vitamin C.

Answer Anticipation:
This is a logical force issue. Look at the quantification: "less likely" to get a cold is a weak statement. "Probably" didn't take Vit. C is a statement with moderate strength. A weak premise can't hold up a moderate conclusion. So, the correct parallel flaw answer here should be another argument that tries to support a moderate conclusion with a weak premise.

Answer Explanation:
Perfect match! A weak premise: "more likely," which could mean 0.1% more likely, is used to support "probably not" in the moderate-strength conclusion. Same fallacy as the stimulus.

Key Takeaway:
If you only remember one thing about logical force, make it that any logical force word that boils down to some or somewhat could mean anything from "at least one" to "all." "Less likely" in the stimulus could mean anything from the risk of a cold decreases by 0.00001% to the risk of a cold falls to zero. It's far too broad a range of possibilities to support a conclusion of any meaningful strength.