PrepTest 133, Section 3, Question 21
Chemist: The molecules of a certain weed-killer are(88 more words not shown)
Which one of the following,(7 more words not shown)
- AIn general, if(30 more words not shown)
- BAlmost all of(36 more words not shown)
- COf the two(23 more words not shown)
- DThe data on(28 more words not shown)
- EData on the(27 more words not shown)
Reading the argument
The soil can break down the part of the weed-killer that actually kills the weeds. That would matter a lot to how well the product works.
There are two forms of the molecule, but only one is effective against weeds. If a soil tends to break down that effective form, the mixture left in the soil will be less useful. If the soil instead tends to break down the ineffective form, the balance will be different. So I can follow why local soil conditions matter to performance.
But why assume the data are misleading? Maybe the researchers already tested a range of soils and accounted for those differences. Variation in the real world is a reason to design the studies carefully; it doesn't establish that the studies failed to do so.
What we’re looking for
To strengthen the argument, show us a mismatch. I'd expect evidence that the soil conditions used to produce the data differ from the conditions where the weed-killer is actually applied. That would connect the known variation to the criticism of the data.
Working the answers
- A
We already know that this weed-killer has one effective form and one ineffective form. Learning that this pattern is common among other weed-killers doesn't tell us whether the data on this particular product properly account for the way its two forms behave in soil. The missing issue is the quality of these data.
- BCorrect
Almost all the data come from studies where the forms are equally concentrated and equally likely to break down. But the passage says actual local soils usually favor the breakdown of one form over the other, producing widely varying concentrations.
That is the mismatch we wanted. A balanced laboratory setting could give results that fail to reflect what happens when the effective form disappears faster in one soil or persists better in another. Because almost all the data come from that setting, the concern extends to much of the data, as the conclusion claims.
- C
This tells us which form is more concentrated in most local soils. It doesn't tell us whether the studies accurately reflected those conditions. Researchers could have incorporated exactly that pattern into their testing. A fact about the application conditions alone doesn't establish a mismatch with the data.
- D
This weakens the concern. Testing a variety of soils similar to those where the product is used is a way to account for the variation the chemist describes. Rather than exposing a gap between the studies and their application, D gives us a reason to trust that the studies reflect relevant conditions.
- E
Perhaps studying just one form would produce misleading data. But are these data based only on one form? We aren't told. E describes a problem that a certain kind of study would have without establishing that the studies behind this conclusion have that feature. B directly describes where the actual data came from.
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