#4- Among the various models of Delta vacuum cleaners, one

[Robert Carroll]

ashpine17,

That's fine because the conclusion itself is weak. The author's conclusion is denying that one factor alone is sufficient to determine how effectively a model cleans. Literally any other factor having any impact on that efficacy will prove the conclusion.

Robert Carroll

[saiffshaikhh@gmail.com]

How is A better than E? I clearly misunderstood the conclusion.

[Jeff Wren]

Hi saiffshaikhh,

The conclusion is the first sentence of the stimulus. It's critical to understand what this conclusion is saying (and implying). It states that one cannot determine the cleaning effectiveness of the vacuum cleaner just based on the power of the motor. What this indicates is that there is (at least one) other factor that affects the cleaning effectiveness besides the motor.

The premise (the second sentence in the stimulus) states that the dust filtration systems vary considerably in efficiency. If we knew that dust filtration systems affect the cleaning effectiveness of the vacuum, then this would be an additional factor (besides the motor) that would impact the overall cleaning effectiveness of the vacuum. This, in turn would justify the conclusion that one cannot determine the cleaning effectiveness of the vacuum cleaner just based on the power of the motor because there would be at least one other factor (the efficiency of the dust filtration systems) that would also need to be known.

Answer A perfectly bridges the logical gap in the argument and justifies the conclusion. If you read the premise, then add Answer A, then read the conclusion, the argument should make logical sense.

Answer E states that one needs to know the motor's power to determine the cleaning efficiency of the vacuum. This does not justify the conclusion, which is about what else/what other factors one needs to know (besides the motor) to determine cleaning efficiency.