Advertisement: Most power hedge trimmers on the market

OFFICIAL EXPLANATION

As with all questions, you must identify the conclusion of the argument. The conclusion states that if you buy a Bolter’s power hedge trimmer, you know the trimmer is safe. In the question stem, we are asked to evaluate the truth of this conclusion. Each answer choice is then posed in the form of a question. The answer choice that is correct will contain the question that, when answered, will reveal whether the conclusion is strong or weak.

In order to understand the application of the Variance Test, we will look at each answer choice in succession and thus we will not perform an initial analysis of the argument (on the LSAT we would analyze the stimulus closely). Also note that on the test we would not apply the Variance Test to each answer choice, only to the Contenders. For teaching purposes, we will apply the Variance Test to each answer in an effort to give you the best possible understanding of how the technique works.

Answer choice (A) asks if National Laboratories has performed tests on other machines from Bolter Industries. To apply the Variance Test, we should supply different and opposing answers to the question posed by the answer choice. First, try the answer “No.” With this answer, would the fact that National Laboratories did not perform safety test on other Bolters machines affect the safety of the Bolter’s hedge trimmer? No—this does not help us evaluate the safety of the hedge trimmer. What if the answer was “Yes” ? Would the fact that National Laboratories performed safety tests on other Bolters machines affect the safety of the Bolter’s hedge trimmer? Not at all. So, regardless of how we respond to the question posed in answer choice (A), our view of the conclusion is the same—we do not know whether the claim that the hedge trimmer is safe is good or bad. According to the Variance Test, if the answer is correct, then supplying opposite answers should yield different views of the conclusion. Since our assessment of the conclusion did not change, the Variance Test tells us that this answer is incorrect.

The question in answer choice (B) is, “How important to the average buyer of a power hedge is safety of operation?” Again, apply the Variance Test and supply opposite answers to the question in the answer choice. In this case, try “Very Important” and “Not Important.” If safety of operation is very important to a buyer of hedge trimmers, would that affect whether the Bolter’s hedge trimmer itself is safe? No. Let’s look at the opposite side: if safety of operation is not important at all to a buyer of hedge trimmers, would that affect whether the Bolter’s hedge trimmer itself is safe? No. Because our view of the validity of the conclusion does not change when we consider different responses to the question posed in answer choice (B), the Variance Test tells us that answer choice (B) is incorrect.

The question in answer choice (C) is, what were the results of the tests of Bolter’s hedge trimmer? Using the Variance Test, supply one response that says, “Bolter’s hedge trimmer failed the safety test.” If this is true, then the conclusion is unquestionably weakened. Now supply a response that says, “Bolter’s hedge trimmer passed the safety test.” If this is true, then the conclusion is strengthened. So, depending on the answer supplied to the question posed in answer choice (C), our view of the validity of the argument changes: sometimes we view the conclusion as stronger and other times as weaker. Therefore, according to the Variance Test, this is the correct answer. In this instance, the Variance Test reveals the flaw in the argument: the author simply assumed that being tested means safety is assured. Nowhere in the argument did the author mention that the hedge trimmer passed the tests, and the Variance Test reveals this flaw.

In answer choice (D), “Yes” and “No” responses do not change our view of the argument, and answer choice (D) is incorrect.

In answer choice (E), “Yes” and “No” responses do not change our view of the argument, and answer choice (E) is incorrect.

The key thing to note is that the Variance Test is applied according to the nature of each answer choice. Thus, with some answer choices we might supply responses of “Yes” and “No,” and other answer choices might require responses of “0%” and “100%,” or “Very Important” and “Not Important.” But, in each case, the answers we supply are opposites, and the correct answer is always the one that changes your view of the validity of the conclusion when those different responses are supplied. If your view of the argument does not change, then the answer choice is incorrect.

Keep in mind that the Variance Test should only be applied to the contending answer choices. In the discussion above we applied it to every answer choice, but we did this simply to show how to effectively apply the Variance Test. During the actual test you would only want to apply the Variance Test to two or three answer choices at most.
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Bolter Industries trimmer tested by National Laboratories------------------so----------------> Safety

There is an obvious gap between test results published by Bolter Industries and the safety standards of the trimmers.

So, (C) is definitely the answer !!
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Power hedge trimmer does its job. But may cause injury to untrained operators. BI's hedge trimmers are tested by NL, which is a trusted safety company. So BI's hedge trimmers are safe.
To evaluate the argument, we have to check whether the BI's hedge trimmers are really safe to be used even by untrained operators.

(A) Has National Laboratories performed safety tests on other machines made by Bolter Industries? - Incorrect - Irrelevant
(B) How important to the average buyer of a power hedge trimmer is safety of operation? - Incorrect - We are not concerned about the average buyers importance to safety. We are concerned about the safety of BI's hedge trimmer.
(C) What were the results of National Laboratories’ tests of Bolter Industries’ hedge trimmer? - Correct - If the results were positive then its safe. If not then its not safe to be used.
(D) Are there safer ways of trimming a hedge than using a power hedge trimmer? - Incorrect - Irrelevant
(E) Does any other power hedge trimmer on the market do a better job of trimming hedges than does Bolter Industries’ hedge trimmer? - Incorrect - Irrelevant

Answer: C

C, this question is prepared by CR bible powerscore, a reliable source for gmat, not just LSAT.
PLease specify the source of the question.

I'd go with C. If the results are bad, you definitely don't buy a product the usage of which is safe.

Conclusion : I buy BHT then I get surety that BHT is safe.

Pre-think: Why BHT is safe. Because BHT has been tested by national Laboratories or Because BHT has passed national laboratories test :D.

Option C fills the gap.

(C) What were the results of National Laboratories’ tests of Bolter Industries’ hedge trimmer? - Correct - If the results were positive then its safe. If not then its not safe to be used.

The analysis of the argument is 'if you buy a power hedge trimmer from Bolter then you are buying the trimmer whose safety is assured" because it testing for trimmers manufactured by Bolter is done by National Laboratories which is the most trusted brand. We are now asked to evaluate the argument. Let's look at options


(A) Has National Laboratories performed safety tests on other machines made by Bolter Industries? - it does not matter and is not in any way related to the argument
(B) How important to the average buyer of a power hedge trimmer is safety of operation? - Not related to the argument
(C) What were the results of National Laboratories’ tests of Bolter Industries’ hedge trimmer? - If results are good conclusion will be strengthened and if results are bad it would be weakened, thus is helpful to evaluate the argument
(D) Are there safer ways of trimming a hedge than using a power hedge trimmer? - If yes then it weakens the argument but if no then it does nothing to the argument, so move away from this answer choice
(E) Does any other power hedge trimmer on the market do a better job of trimming hedges than does Bolter Industries’ hedge trimmer? - It talks about trimming better but does not takes safety into the account, so not helpful to evaluate

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