Q4 - A study claims that the average

[ginsburgb]

I narrowed this down to B and D, but I chose D. B is correct so I'm hoping you can clarify why. When rereading answer D, I think it is because it reverses the last sentence, but is that correct thinking? Thanks.

[bbirdwell]

Well it's not exactly a reversal. (D) is incorrect because the argument doesn't state that the random fluctuations "typically" last 10 years -- it merely says that periods when the average temp goes up have lasted up to 10 years and yet not been permanent.

The point of that statement is to counter the first sentence, which suggests that, since avg temps have risen for 5 years, the change is permanent.

That's why (B) is correct.

[ManhattanPrepLSAT1]

A study claims that the average temperature on Earth has permanently increased, because the average temperature for the last five years has been higher than any previous yearly average on record. The stimulus then calls into question whether the evidence is sufficient to establish the study’s conclusion.

Correct Answer
Answer choice (B) correctly states that the evidence offered by the study is insufficient to establish its conclusion.

Incorrect Answers
(A) is unsupported. This answer is far too strong.
(C) is unsupported. No predictions about future weather are suggested within the information.
(D) is unsupported. We know that periods of record highs of up to 10 years are often part of random fluctuations _ this does not support the claim that random fluctuations typically last less than ten years.
(E) is unsupported. According to the information there could be increases in the average temperature that are not part of random fluctuations.

[lym]

Thank you tutors !

I also got this wrong. But now I can see that B is more close to the main point the author intends to make.

A minor question:

Is "the average temperature each year for the last five years has been higher than any previous yearly average on record" the same thing as "five successive years of increasing annual average temperature"? It seems to me that in the former case, each of the yearly averages does not necessarily exceeds It's preceding year, while the latter description simply means "continuous growth".

Just a minor doubt.

[ManhattanPrepLSAT1]

Is "the average temperature each year for the last five years has been higher than any previous yearly average on record" the same thing as "five successive years of increasing annual average temperature"? It seems to me that in the former case, each of the yearly averages does not necessarily exceeds It's preceding year, while the latter description simply means "continuous growth".

Good question, and no they're not exactly the same.

(A) "five successive years of increasing annual average temperature" only means that during a five-year period, each year was hotter than each of the previous years in that period.

(B) "the average temperature each year for the last five years has been higher than any previous yearly average on record" goes further. This means that each year not only was the average temperature hotter than the previous years in that five-year period, but also that each year was hotter than any previous year in recorded history.

So while (B) implies (A), it's NOT true that (A) implies (B). Hope that helps!