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

erfrosen
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"Among the various models of Delta vacuum cleaners, one cannot accurately predict how effectively a particular model cleans...

The argument's conclusion is properly drawn if which one of the following is assumed?"

I got the correct answer of A, so I understand the point of the question, but am a little unsure of what the actual "conclusion" is as referred to in the question. Would it be:
["one cannot accurately predict how effectively a particular model cleans simply by determining how powerful its motor is"] or ["The efficiency of dust filtration systems various significantly, even between models of Delta vacuum cleaners equipped with identically powerful motors"]?

Thanks!!
Charlie Melman
PowerScore Staff
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Hi erfrosen,

The conclusion of this argument is that "one cannot accurately predict how effectively a particular model [of Delta Vacuum cleaners] cleans simply by determining how powerful its motor is."

We know this because the second sentence (the premise) provides support for the first (thus making it the conclusion). Since vacuums that have identically powerful motors can differ in another important respect (the efficiency of their dust filtration systems), then determining motor power is not sufficient to determine cleaning effectiveness. (Of course, there's a gap here, and you correctly identified that gap by choosing answer choice (A).)

Hope this helps!
LSAT2018
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I just wanted to make sure why answers (A) and (B) are not Mistaken Negation/Mistaken Reversals of the stimulus. I was left with these two answers, and was wondering how to distinguish them.
knowledgeconsumer
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Location: Dehli, India

What models are determined by the term "Delta vacuum cleaners"? Is the iRobot Roomba 690 related to it? I'm also get stacked between (A) and (B) answers and didn't get it completely.
Rachael Wilkenfeld
PowerScore Staff
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Hi LSAT2018 and knowledgeconsumer,

Since both of you have similar sorts of questions, I will address them together. I would not look at this as a conditional stimulus. When we read the stimulus, we see a premise that the efficiency of dust filtration systems varies among Delta vacuum cleaners even with identically strong motors. The author draws the conclusion that you can't judge how efficiently the Delta vacuums clean based only on the strength of the motor. One way to think about Justify questions is by looking for a logical leap between the premise(s) and the conclusion. Here, there's a big jump from efficiency of dust filtration systems to efficiency of cleaning. So we will need to link those two ideas to show that the dust filtration system matters for the cleaning efficiency of a vacuum. Answer choice (A) does so. Answer choice (B) on the other hand tries to link the power of a motor to the power of the dust filtration system. But that isn't really relevant here, because the stimulus is talking about vacuums with identically strong motors. As to what models are included under Delta vacuum cleaners, I don't think it is really important. Both the stimulus and all the answer choices refer to the same items (Delta vacuum cleaners) consistently, so we don't have to look beyond the term to decide if any other sort of vacuum would fit.

Hope that helps!
Rachael