Records from 1850 to 1900 show that in a certain region, babies' birth weights each year varied with the success of t...

Jacob-R on October 24, 2018

Answer D is incorrect because it states that the argument proceeds by inferring the existence of “a common cause” of two phenomena. In the passage, there are two phenomena discussed: crop success and birth weights. There is no “common cause” of these two phenomena discussed in the passage (the mention of “amount of food” in the final sentence is just a different way of referring to the crop success phenomenon.)

Answer A is correct because, as you correctly note in your question, the author is stating a hypothesis at the end. But this hypothesis is about a correlation between the two phenomena, without any “common cause.”

I hope this helps. Please let us know if you have any more questions.

Aidyn-Carlson on May 28, 2019

Why is this a and not b? And how can I improve on these kinds of questions

Ravi on May 28, 2019

@Aidyn-Carlson,

Happy to help. Let's take a look at (A) and (B).

(B) says, "inferring from the claim that two phenomena have fluctuated
together that one of those phenomena must be the sole cause of the
other."

The argument's conclusion doesn't make the claim that the success of
crops and mothers' access to food is the sole cause of something;
rather, the conclusion instead states that one depends largely on the
other. For this reason, we can get rid of (B).

(A) says, "inferring from a claimed correlation between two phenomena
that two other phenomena are causally connected to one another."

The phenomena that are correlated in the stimulus are birthweights and
crops' success. The phenomena that the argument claims are causally
connected to one another are the health of the babies and the mothers'
availability of food to the mother. In looking at (A), it does a great
job in stating what's going on in the argument in general terms. The
argument is taking a correlation between two things and inferring
causation between two other things, so (A) is the correct answer
choice.

Does this make sense? Let us know if you have any more questions!

Ravi on May 28, 2019

@Aidyn-Carlson, to improve on these questions, you've got to practice a ton. The more you do these questions and diligently review, the better you'll be able to understand how to tackle these well.