Q20 - In the country of Boldavia at present, only 1 percent

[kyuya]

Judging by the stimulus, the older people get, the less left handed people there is. Like wise, the younger the population, the more left handed people there is.

Upon the initial read, I thought it may have something to do with their unique society having changed over time which may have resulted in this discrepancy. However, it turns out to be something else.

I'll start with the wrong answers first:

(B) This does nothing. This type of answer is often the type of answer that can be good for STRENGTHEN type questions that are a bit higher level when there is a cause and effect relationship being discussed. By eliminating an alternative, it can boost your argument. However, this is not the case here. It is simply leaving us with no more information to solve this discrepancy.

(C) Tells us about what is valued, but not about how to solve a discrepancy.

(D) This would address the population as a whole, and in the same way (B) doesn't do anything, this also doesn't do anything. It would effect both men and women the same, but we would know nothing about why there is still a discrepancy that seems to be correlated with age.

(E) This also does nothing. Tells us a fun fact about Boldavia, but again, does nothing to help solve a discrepancy.

So, that leaves us with (A).

(A) This answer choice essentially tells us that men are more likely than women in this society to be left handed. But they also have a shorter life span.

So, shorter life span + more likely to be left handed = more women in the population, and therefore, more right handed people in the population. Since it is related to age, we should expect that the higher up we go in age, the proportion of right handed people should increase, due to the fact women on the whole live longer than men.

We see in the stimulus that this is what is happening. 80 years old is.. well.. old. So we would expect to see less men (lower expected age, remember) and therefore, less left handed people. And that is exactly what's happening.

[MeenaV936]

I still don't understand why D is incorrect. My thinking was that if the percent within each age group increases but the overall proportion does not change, then birth rates must have decreased because if fewer people are being born each year, then it would make sense that the percents within each age group would decrease but the overall proportion would not change. Is D wrong because it says "slowly but steadily"? Please let me know -- thanks!

[ohthatpatrick]

I'm getting a little lost in what you're going for.

This idea in particular:
My thinking was that if the percent within each age group increases but the overall proportion does not change, then ....

It's impossible for the percentage of X to rise while the proportion of X remains the same.

Percent and proportion mean the same thing.
Proportion = percent = fraction

Say you have 10 people, 2 of them left handed, 8 of them right handed.

What proportion of them are left handed?
you could say 2/10 or 20%, since 2/10 = 20% = 20/100

When we're dealing with percents / fractions / ratios / proportions, the absolute raw number doesn't matter.

(D) is talking about whether we have more or fewer babies, in raw number terms, so it won't have any impact on this conversation.

(D) is saying fewer babies are born now than were born 80 years ago.
Let's say it used to be that 10,000 babies were born each year.
Now only 1,000 babies are born each year.

From the stimulus, we know that "the proportion who are born left handed has not increased."

If 20% of those 10,000 babies were left handed 80 years ago,
then 20% of those 1,000 babies just recently born were also left handed.

The paradox is this: "if 20% of those 10,000 babies were left handed, 80 years ago, how come 80 years later ... only 1% of those now-80-year-old 'babies' are left-handed?"

Think of it this way:
At Jackson High, every incoming class of freshman has the same proportion of males (we'll say 50%). However, the sophomore classes are usually 45% male, the junior class is usually 40% male, and the senior class is usually 30% male.

What could explain this?

If males have a higher rate of dropping out of high school than do females, then the further we go into high school, the smaller the proportion of males each class would have.

It wouldn't make any difference if last year's freshman class was 500 people and this year's freshman class was only 400 people.

The raw number of the freshman class is irrelevant, because no matter what the number is, 50% of them are male. And whatever the number is, as THAT freshman class progresses through its sophomore -> junior -> senior years, the percentage of males is that class is getting lower.

Hope this helps.