Self-study
A recent study found that small rats were approximately twice as likely, and large rats only half as likely, to suffer from heart problems than were rats of average size.
"Surprising" Phenomenon
Why are small rats more likely than normal rats to suffer from heart problems, and large rats are less likely than normal to suffer form heart problems?
Objective
This is an EXCEPT question. The four wrong answers will help differentiate small rats from other rats in a way that makes them more likely to have heart problems, or it will help differentiate large rats from other rats in a way that makes them less likely to have heart problems.
16.
Each of the following, if █████ ███████████ ██ ██ ███████████ ██ ███ ███████████ █████ █████ ███████ ████ ███ █████ ███████ ██ ████ ███████
a
Small rats are ████ ██████ ████ █████ ████ ██ ██████ ████ █████ ████████ ████ ████ ██ ██████ ███████ ████ ██ █████ █████████
This deepens our confusion. If small rats are more likely than large rats to die before getting heart problems, then we’d expect the overall rate of heart problems among small rats to be lower than for the other rats, who are more likely to survive to the age of getting heart problems.
b
Small rats generally ████ ███████ █████ ███████ ████ ██ █████ █████ ███████ ████ ███ ████ ██████ ██ ███████ ████ █████ █████████
If small rats have smaller blood vessels, which can be more easily clogged with fat, that’s a potential causal mechanism that could explain the smaller rats’ increased risk of heart problems.
c
The larger a ███ ███ ███ ████ ██████████ ██ ████ ██ ██ █████████ ███████ ███ █████████ ███ ████ █████████ ███ █████████ ████ ███
The smaller ones have more stress, which might lead to increased heart problems. The larger rats have less stress, which might lead to fewer heart problems. And the average rats are in the middle for stress, which might lead to being in the middle for heart problems.
d
In addition to █████ ███ ███████ █████ ██ ████ ██████ ██ █████ █████ ████████████ ██ █████ ██████ ██ ███████████ ██████ ████ ██ ██ ███████████
This tells us malnutrition causes both a weak heart and smaller body size. This could explain why the smaller rats have more heart problems: those rats were more likely to be the malnourished ones.
e
Although large rats ███ ██ ████ ██████ ████ ████ ██ ███████ █████ ████ ████ ██ ██ ████ ████ ██████ ████ █████ █████ █████████ ██ ███████ ██████████████ █████████████
(E) establishes that small rats have less cardiovascular conditioning (meaning conditioning related to the heart) than the average and large rats. This helps explain why small rats have more heart problems than the other groups.