The Variance TestTM

Solving Evaluate questions can be difficult. The nature of the answer choices
allow for separate interpretations, and deciding on a single answer can be
challenging. In order to determine the correct answer choice on a Evaluate the
Argument question, apply the Variance TestTM.
The Variance Test consists of supplying two polar opposite responses to the
question posed in the answer choice and then analyzing how the varying
responses affect the conclusion in the stimulus. If different responses produce
different effects on the conclusion, then the answer choice is correct. If different
responses do not produce different effects, then the answer choice is incorrect.
For example, if an Evaluate the Argument answer choice states “What is the
percentage of people who live near a nuclear plant?” look to test the two most
extreme possibilities: first test the response “0%” for its effect on the conclusion
and then test the response “100%” for its effect on the conclusion. If the answer
choice is correct, one of the percentages should strengthen the argument and
one of the percentages should weaken the argument. If the answer choice is
incorrect, neither response will have an effect on the argument.
Of course, the answer choice does not have to be about percentages for the
technique to work; the Variance Test will work regardless of the nature of the
answer choice. Here are some more example answer choices and Variance Test
responses:
If an answer choice asks “Is the pattern permanent?” first test “Yes” as a
response and then test “No” as a response (remember, you must test
opposite answers). If the answer choice is correct, one response should
strengthen the argument and one response should weaken the argument.
If the answer choice is incorrect, neither response will have an effect on
the argument.
If an answer choice asks “Are corporate or environmental interests more
important?” first test “Corporate interests are more important” as a
response and then test “Environmental interests are more important” as a
response. If the answer choice is correct, one response should strengthen
the argument and one response should weaken the argument. If the
answer choice is incorrect, neither response will have an effect on the
argument.
Now we will use an LSAT question to more fully explore how the question
type works and how the correct answer can be determined by the Variance Test.
Please take a moment to complete the following question:
1. Advertisement: Most power hedge trimmers on the market do an adequate job of trimming hedges, but many power hedge trimmers are dangerous to operate and can cause serious injury when used by untrained operators. Bolter Industries’ hedge trimmer has been tested by National Laboratories, the most trusted name in safety testing. So you know, if you buy a Bolter’s, you are buying a power hedge trimmer whose safety is assured.
The answer to which one of the following questions
would be most useful in evaluating the truth of the
conclusion drawn in the advertisement?
(A) Has National Laboratories performed safety
tests on other machines made by Bolter
Industries?
(B) How important to the average buyer of a
power hedge trimmer is safety of operation?
(C) What were the results of National
Laboratories’ tests of Bolter Industries’
hedge trimmer?
(D) Are there safer ways of trimming a hedge than
using a power hedge trimmer?
(E) Does any other power hedge trimmer on the
market do a better job of trimming hedges
than does Bolter Industries’ hedge trimmer?

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.