Causality and Strengthen Questions

Because Strengthen and Weaken questions require you to perform opposite
tasks, to strengthen a causal conclusion you take the exact opposite approach
that you would in a Weaken question.
In Strengthen questions, supporting a cause and effect relationship almost
always consists of performing one of the following tasks:
A. Eliminate any alternate causes for the stated effect
Because the author believes there is only one cause (the stated cause in
the argument), eliminating other possible causes strengthens the
conclusion.
B. Show that when the cause occurs, the effect occurs
Because the author believes that the cause always produces the effect,
any scenario where the cause occurs and the effect follows lends
credibility to the conclusion. This type of answer can appear in the form
of a example.
C. Show that when the cause does not occur, the effect does not occur
Using the reasoning in the previous point, any scenario where the cause
does not occur and the effect does not occur supports the conclusion.
This type of answer also can appear in the form of a example.
D. Eliminate the possibility that the stated relationship is reversed
Because the author believes that the cause and effect relationship is
correctly stated, eliminating the possibility that the relationship is
backwards (the claimed effect is actually the cause of the claimed cause)
strengthens the conclusion.
E. Show that the data used to make the causal statement is accurate, or
eliminate possible problems with the data
If the data used to make a causal statement is in error, then the validity of
the causal claim is in question. Any information that eliminates error or
reduces the possibility of error will support the argument.
Take a moment to consider each of these items as they will reappear in the
discussion of causality and Assumption questions—the approach will be
identical for that combination.
Please take a moment to complete the following problem:
3. Modern navigation systems, which are found in most
of today’s commercial aircraft, are made with
low-power circuitry, which is more susceptible to
interference than the vacuum-tube circuitry found in
older planes. During landing, navigation systems
receive radio signals from the airport to guide the
plane to the runway. Recently, one plane with
low-power circuitry veered off course during landing,
its dials dimming, when a passenger turned on a
laptop computer. Clearly, modern aircraft navigation
systems are being put at risk by the electronic
devices that passengers carry on board, such as
cassette players and laptop computers.
Which one of the following, if true, LEAST
strengthens the argument above?
(A) After the laptop computer was turned off, the
plane regained course and its navigation
instruments and dials returned to normal.
(B) When in use all electronic devices emit
electromagnetic radiation, which is known to
interfere with circuitry.
(C) No problems with navigational equipment or
instrument dials have been reported on
flights with no passenger-owned electronic
devices on board.
(D) Significant electromagnetic radiation from
portable electronic devices can travel up to
eight meters, and some passenger seats on
modern aircraft are located within four meters
of the navigation systems.
(E) Planes were first equipped with low-power
circuitry at about the same time portable
electronic devices became popular.
The conclusion of the argument is based on the causal assumption that
electronic devices cause a disturbance in low-power circuitry, creating an
obvious danger:
ED = electronic devices
I = interference with low-power circuitry
C                               E
ED--------------------------> I
The question stem is a StrengthenX (remember, Least works like Except in
question stems) and thus the four incorrect answers will each strengthen the
argument. As you attack the answer choices, look for the five causal
strengthening answer types discussed earlier.
Answer choice (A): This answer choice strengthens the argument by showing
that when the cause is absent, the effect does not occur (Type C). Once the
laptop was turned off, the cause disappeared, and according to the author’s
beliefs, the effect should then disappear as well.
Answer choice (B): This answer strengthens the argument by showing that the
data used to make the conclusion is accurate (Type E). By stating that all
electronic devices emit radiation, the answer choice closes a hole in the
argument.

Answer choice (C): This answer choice strengthens the argument by showing
that when the cause is absent, the effect does not occur (Type C).
Answer choice (D): This answer strengthens the argument by showing that the
data used to make the conclusion is accurate (Type E). By showing that
radiation can travel far enough to reach the cockpit, the cause is confirmed as
possible.
Answer choice (E): This is the correct answer. The fact that the circuitry and
electronic devices became popular at the same time does not offer any
supporting evidence to the contention that the electronic devices cause the
interference with the low power circuitry. This answer has no effect on the
argument and is therefore correct.
Please take a moment to complete the following problem:
4. Amphibian populations are declining in numbers
worldwide. Not coincidentally, the earth’s ozone
layer has been continuously depleted throughout the
last 50 years. Atmospheric ozone blocks UV-B, a
type of ultraviolet radiation that is continuously
produced by the sun, and which can damage genes.
Because amphibians lack hair, hide, or feathers to
shield them, they are particularly vulnerable to UV-B
radiation. In addition, their gelatinous eggs lack the
protection of leathery or hard shells. Thus, the
primary cause of the declining amphibian population
is the depletion of the ozone layer.
Each of the following, if true, would strengthen the
argument EXCEPT:
(A) Of the various types of radiation blocked by
atmospheric ozone, UV-B is the only type
that can damage genes.
(B) Amphibian populations are declining far more
rapidly than are the populations of
nonamphibian species whose tissues and
eggs have more natural protection from
UV-B.
(C) Atmospheric ozone has been significantly
depleted above all the areas of the world in
which amphibian populations are declining.
(D) The natural habitat of amphibians has not
become smaller over the past century.
(E) Amphibian populations have declined
continuously for the last 50 years.
This question is much more difficult than the previous question, in part because
one of the wrong answer choices is very attractive.
The conclusion of the argument is a causal statement that the depletion of the
ozone layer is the primary cause of the declining amphibian population:
DO = depletion of the ozone layer
DA = decline of amphibian population
C                               E
DO------------------------> DA
This conclusion is based on the fact that the ozone layer blocks harmful UV-B
radiation, which amphibians are vulnerable to in both adult and egg form.
Although the argument mentions UV-B radiation, which may sound impressive,
the structure of the reasoning is easy to follow and no knowledge of the
radiation is needed. The conclusion is clearly stated and easy to spot due to the
indicator “thus.” The question stem is a StrengthenX and therefore the four
incorrect answers will each strengthen the argument. As with the previous
question, look for answers that fit the five causal strengthening answer types
discussed earlier.
Answer choice (A): This is the correct answer. The answer fails to shed any
light—positive or negative—on the connection between the ozone depletion
and the amphibian population decline. Because the argument is concerned with
the damage done by UV-B radiation, the fact that UV-B is the only damaging
type of radiation blocked by ozone is irrelevant.
Answer choice (B): This answer choice strengthens the argument by showing
that when the cause is absent in nonamphibian populations, the effect does not
occur (Type C).
Answer choice (C): This answer strengthens the argument by showing that the
areas of ozone depletion and amphibian decline match each other, thereby
affirming the data used to make the conclusion (Type E).
Answer choice (D): This was the answer most frequently chosen by test takers.
This answer choice strengthens the argument by eliminating an alternate cause
for the effect (Type A). Had the natural habitat become smaller over the years
(from say, human encroachment or climatic change) then that shrinkage would
have offered an alternate explanation for the decline in the amphibian
population. By eliminating the possibility of habitat shrinkage, the stated cause
in the argument is strengthened.
Answer choice (E): This answer strengthens the argument by showing that the
decline of the amphibians has mirrored the decline of the ozone layer, thereby
affirming the data used to make the conclusion (Type E).