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- Fri Jan 21, 2011 12:00 am
#27282
Complete Question Explanation
Strengthen—#%. The correct answer choice is (A)
This question is also a very challenging question, as only about 30% of test takers select the correct answer. The argument in the stimulus is that there has been a dramatic increase in the number of people over the age of 65 in the region in the last 10 years. This conclusion is based on the observation that the average age of people in the region has increased from 52 to 57.
Keep in mind that averages can actually be increased by one of two possible causes: an increase in the number of things above the original average, or a decrease in the number of things below the original average (averages can be lowered by the exact opposite ideas). Here, the author concludes that the average age increase was caused by an increase in the things above the average (more old people), meaning that he/she assumes the other cause—fewer young people—did not occur. Since we are asked to strengthen this causal argument, we need to eliminate the potential alternate cause of the average age increase and show that there are NOT fewer young people in the region now.
Answer choice (A): This is the correct answer choice. As mentioned above, to strengthen a causal argument with two possible causes, you should look for an answer that eliminates the cause you do not want. By stating that there are now more young people, answer choice (A) eliminates the possible cause of fewer young people, and makes it more likely that the cause we want—more old people—is the reason that the average age has gone up. Put another way: if there are now more young people, we would expect the average age to go down. Since it has still gone up, it seems even more likely that a significant number of old people are now in the region, increasing the overall average age. So the conclusion would be strengthened.
Answer choice (B): This is the most frequently chosen incorrect answer, but it actually weakens the argument. As discussed previously, the alternate (and unwanted) explanation for an increase in the average age in the region would be fewer young people, as fewer young people would cause the average age to rise with or without more old people. So if the birth rate has decreased significantly, that means that there are now fewer young people and the average age would be expected to increase. Since this answer choice provides an alternate cause for the average age increase (i.e. not more old people as the stimulus states, but fewer young people instead), it hurts our argument and is incorrect.
Answer choice (C): There is no way to know if a change in the number of people in the region (positively or negatively) would have any impact on the number of people over the age of 65, so this answer choice cannot be thought to have an effect on the argument.
Answer choice (D): Again, an increase in the number of people in the region cannot be known to have any impact on the number of people over the age of 65, so like answer choice (C), this answer has no effect on the argument.
Answer choice (E): Comparing the average age of the region to that of surrounding regions does not affect our opinion of the possibility that there are now more people over 65 in the region than there were 10 years ago. That is, just because the average age is higher than that of surrounding regions does not mean that the number of people over the age of 65 has increased.
Strengthen—#%. The correct answer choice is (A)
This question is also a very challenging question, as only about 30% of test takers select the correct answer. The argument in the stimulus is that there has been a dramatic increase in the number of people over the age of 65 in the region in the last 10 years. This conclusion is based on the observation that the average age of people in the region has increased from 52 to 57.
Keep in mind that averages can actually be increased by one of two possible causes: an increase in the number of things above the original average, or a decrease in the number of things below the original average (averages can be lowered by the exact opposite ideas). Here, the author concludes that the average age increase was caused by an increase in the things above the average (more old people), meaning that he/she assumes the other cause—fewer young people—did not occur. Since we are asked to strengthen this causal argument, we need to eliminate the potential alternate cause of the average age increase and show that there are NOT fewer young people in the region now.
Answer choice (A): This is the correct answer choice. As mentioned above, to strengthen a causal argument with two possible causes, you should look for an answer that eliminates the cause you do not want. By stating that there are now more young people, answer choice (A) eliminates the possible cause of fewer young people, and makes it more likely that the cause we want—more old people—is the reason that the average age has gone up. Put another way: if there are now more young people, we would expect the average age to go down. Since it has still gone up, it seems even more likely that a significant number of old people are now in the region, increasing the overall average age. So the conclusion would be strengthened.
Answer choice (B): This is the most frequently chosen incorrect answer, but it actually weakens the argument. As discussed previously, the alternate (and unwanted) explanation for an increase in the average age in the region would be fewer young people, as fewer young people would cause the average age to rise with or without more old people. So if the birth rate has decreased significantly, that means that there are now fewer young people and the average age would be expected to increase. Since this answer choice provides an alternate cause for the average age increase (i.e. not more old people as the stimulus states, but fewer young people instead), it hurts our argument and is incorrect.
Answer choice (C): There is no way to know if a change in the number of people in the region (positively or negatively) would have any impact on the number of people over the age of 65, so this answer choice cannot be thought to have an effect on the argument.
Answer choice (D): Again, an increase in the number of people in the region cannot be known to have any impact on the number of people over the age of 65, so like answer choice (C), this answer has no effect on the argument.
Answer choice (E): Comparing the average age of the region to that of surrounding regions does not affect our opinion of the possibility that there are now more people over 65 in the region than there were 10 years ago. That is, just because the average age is higher than that of surrounding regions does not mean that the number of people over the age of 65 has increased.
The author's objective, however, is to strengthen the conclusion that the averages went up because of an increase in the number of people above the original average:
Average age went up