PTA.S1.Q20

PrepTest A - Section 1 - Question 20

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In the country of Boldavia at present, only 1 percent of 80-year-olds are left-handed, whereas 10 percent of 50-year-olds and 15 percent of 20-year-olds are left-handed. ███ ████ ███ ████ ██ ██████ ███ ██████████ ██ ██████████ ███ ███ ████ ███████████ ███ ███ ██████████ ███ ████ █████████ █████████ ██████ ███████████████ █████████ ███ █████████ ████████

Analysis: Resolve, Reconcile, Explain

The stimulus comments on a surprising phenomenon: only 1% of Boldavian 80-year-olds are left-handed, compared to 10% of 50-year-olds and 15% of 20-year-olds, even though there has been no change over the last 80 years in the proportion of Boldavians born left-handed or in Boldavian attitudes toward left-handedness.

So we're trying to explain why the proportion of left-handed Boldavian 80-year-olds is so much smaller than the proportion of left-handed Boldavians at younger ages. The stimulus has already ruled out changes in the proportion of left-handedness at birth and changes in cultural attitudes as explanations. But if, for some reason, being left-handed was correlated with a higher risk of early mortality, this could explain why the proportion of left-handed Boldavians declines with age: left-handed Boldavians might be dying earlier than their non-left-handed peers.

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20.

Which one of the following, ██ █████ ████ █████ ██ ███████ ███ █████████ ██ █████████ ██ ███████████████ █████ ███████████

a

In Boldavia, where ███ ████ █ ███████ ███████ ████ ██████████ ████ ██ ██████ ███████████████ ██ ████ ██████ █████ █████ ████ █████ ████
Correct. Even though (A) might seem to focus on a gender difference that we didn't discuss in our analysis, it ultimately says what we were saying in our analysis: left-handedness is correlated with earlier mortality, because left-handedness is more common among Boldavian men than among women, and men in Boldavia have a shorter life expectancy. If more men than women are left-handed, and men tend to die earlier, this helps explain why the percentage of left-handed Boldavians goes down in older age groups.
71%
b

In Boldavia, left-handed ██████ ███ ██ ████ ██████ ████ ████████████ ██████ ██ ██ ████████ ██ ██████████
Incorrect. (B) actually makes the phenomenon in the stimulus even harder to resolve, by ruling out one potential explanation: left-handed Boldavians are more prone to accidents than right-handed ones, which could help explain why fewer left-handed Boldavians survive to older ages.
2%
c

Ambidexterity is highly ██████ ██ █████████
Irrelevant. Even if (C) is true, it does nothing to help explain specifically why the proportion of left-handed Boldavians seems to decline in older age groups. According to the stimulus, if ambidexterity is valued now, it seems likely that ambidexterity was valued to the same degree over the last 80 years. So this fact doesn't help us understand the differences between the percentages of left-handed Boldavians at different ages.
6%
d

The birthrate in ████████ ███ █████████ ██████ ███ ████████ ████ ███ ██████ ██ ███ ████ ██ ██████
Irrelevant. This means that fewer people are being born overall in Boldavia. But the stimulus isn't talking about raw numbers of people: it's talking about the proportion of people who are left-handed at different ages. And the stimulus explicitly tells us that the proportion of Boldavians born left-handed hasn't significantly changed over the last 80 years, which can still be true even if the raw number of Boldavians being born is declining. So (D) doesn't help explain the declining proportion of left-handed Boldavians among older age groups.
18%
e

Left-handed people have █████ █████████ ███ ████ ████ ██ ███████ ██ ███ ██████████ ██ █████████
Incorrect. Knowing that 18% has been the historical limit of left-handed Boldavians as a percent of the population doesn't help us explain why the percentage of left-handed Boldavians seems to go down in older age groups.
2%

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