LR Question 25 Explanation
QUESTION TEXT: The populations of certain species of amphibians have…
QUESTION TYPE: Necessary Assumption
CONCLUSION: We can’t know if the recent decline of certain amphibian species is due to pollution.
REASONING: Weather variations can also cause changes in most amphibian populations. Amphibian populations decreased quite a bit recently.
ANALYSIS: This seems like a good argument. But there is a flaw of course – otherwise this wouldn’t be a necessary assumption question.
Weather causes variations, but there are surely limits. If amphibian populations declined far past normal changes caused by weather, then we could suspect pollution.
The other possible flaw is that the argument only said that most amphibian species can decline due to weather. If there are some amphibian species that don’t decline from weather, then we could be surer that those species declined from pollution.
Note that the wrong answers make odd linkages between elements from the stimulus. It’s very, very rare for this type of answer to be right. Mostly they are used to slow you down, because the brain interprets familiar concepts as possible answers.
___________
- CORRECT. Negate this and the argument falls apart.
Negation: The amphibian species that declined are among those species whose populations do not change much with the weather. - The argument is stronger if this isn’t true.
Negation: Declines due to weather variation are always as large as those attributed to pollution. - This is hardly necessary. It’s possible industrial pollution caused most of the decline but weather contributed a bit. Real world causes are rarely exclusive.
Negation: It’s possible that both pollution and weather had some contribution to the decline. - The argument is talking about the causes of the past decline, not what will happen in the future.
- Why would this be necessary? The scientists made no link between pollution and weather.
Question about 75 s3/25,
I am thinking, C, pollution or weather, but not both, cause population dec,
must be false, it can lead to possible to differentiate; because if it is pollution caused then it is not weather caused.
But it cannot be true, because it is too limited, like it is SA to it is possible to differentiated.
one of reason it is impossible, because it is equal likely to be either pollution or weather, and it can be both.
The reason they said it impossible to differentiate, according to A, is pollution caused population decline does not belong to weather caused population dec. which is just part of C, C goes further saying, weather caused population and no pollution caused population decline.
I am still trying to wrap my head around this argument.
C is saying that the argument assumes it cannot be both pollution or weather. But the argument doesn’t assume this.
The argument is saying that we don’t know for sure that it’s pollution. It COULD be all pollution. It could also be all weather, or a mix of the two. All the argument is saying is that we can’t definitively say that it’s pollution.
Necessary assumption questions aren’t the same as must be true/false questions. It is possible for an answer to be true/false but not the necessary assumption for the argument.
I hope this helped!
Why did you negate one of the “NOT”‘s in A and not both?
If there are two negatives, you negate the statement by negating just one. Consider this:
I like Disney –> I do not like Disney
I don’t not like Disney –> I don’t like Disney
Both the original sentence and the double negative form mean basically the same thing. I like = I don’t not like. Thus, they negate to the same thing.
If you remove both negatives you actually keep the sentence largely the same.
(Technically I don’t not like can be neutral, but it’s at least consistent with liking something)
Note: This is an old comment but I wanted to clarify the point.
I don’t have a problem with the analysis or answers with this, I’m just going to nitpick one of the explanations of the wrong answers. In my own analysis, I wrote that D would actually weaken this argument. Wouldn’t this establish causation of population fluctuation on behalf of industrial pollution for the “certain species”? In my view, it doesn’t shed much light on how weather effects the populations, but it does show that industrial pollution has a discernible effect on population levels of these frogs, thus adding a bit of strength to the idea that the decline was due to pollution?
Or should we view conditionals concerning the future not to hold much water when we’re observing a past phenomenon on the LSAT, as you stated?
If this conditional were referring to the past, then yes it could (weakly) weaken the argument. But it’s referring to a future state of affairs.
I say it’s not a great way to weaken the arguent because (D) is only suggesting a correlation — it’s still not good enough proof that industrial pollution is a cause. But, it might provide some more reason to believe that industrial pollution might be the issue at play here.