Q25 - A letter submitted to the editor

[slimjimsquinn]

Can someone break this down?

Before I moved on to the AC I guessed the flaw to be ignoring the likelier possibility that Dr. Shirley Martin was a part of the 5% of women professors.

Things got messy as i went down to the answer choices. I was swayed by D because of the similarity in language.

I also couldn't understand the significance of the the "19 to 1" part of the stimulus. Are they using that probability to compare with the 5%?

Thanks in advance!

[ManhattanPrepLSAT1]

You are correct about the significance of the phrase "19 to 1." 1 out of 20 is the same as 5%. The flaw in the argument is that the editor failed to consider relevant information contrary to the conclusion reached. Shirley's name should have given the editor some indication that the letter was more likely written by a woman. Rather than only considering the frequency of women professors at major North American medical schools, the editor should have also considered the frequency of women named Shirley. This flaw is repeated in answer choice (E) in that Emily should not have considered only the percentage of animals at the zoo that are mammals, but also the percentage of animals that fly between trees that are mammals.

Incorrect Answers
(A) commits a different flaw where what is true of the average is taken to be true of any subset of the whole from which the average is calculated.
(B) is not totally unreasonable, without any further information about those manuscripts.
(C) switches the direction of proportionality. It could be the case that 100% of Latin scholars graduated, while they made up only a small proportion of the entire graduating class.
(D) commits the flaw of assuming that the small planes were the planes built by UBC that failed to meet government standards.

[ywan1990]

For this question, I think there is an easier flaw that helps me pick up the correct answer. The evidence which the editor uses is 'the probability of having a female professor at such schools', while the conclusion is about the probability of having a female professor at a specific school (which belongs to 'such schools' of course)

The editor is committing one common flaw type: he is applying what is true to the 'whole' to a specific individual within the whole.

Now (E) is doing exactly the same. The probability of having a mammal in a wildlife preserve may not be equivalent to the probability of having a mammal in the specific case of an animal 'flying between two trees'.

[WaltGrace1983]

(A) Assumes that what is true for the average is true for one part of the average. I like the way Matt put that. In other words, even if we HAVE TO have every 19/20 computers be used for gaming (95%), maybe there will be 100 computers sold today and so 5 computers sold for something other than games can be sold sequentially - one after the other.

(B) I feel like this is still similar to (A). I think that this is still taking a piece of the whole when the average is about the entire whole. Maybe there are 100 submissions in a month and only 5 will be selected each month. Couldn't all 5 get selected in the first week while the other three weeks have nothing accepted?

(C) This is, I think, taking a statistic and equating it to a rigid cutoff. For example, if I said that only 5% of every Yale student graduated summa cum laude in 2014, does that mean that there was a strict 5% cutoff in which there can ONLY BE 5% graduating summa? I'd say no.

(D) Assumes no overlap. I stand by this one. Maybe the small planes were also met govt. standards.

(E) We are given this statistic saying that less than 5% of the animals are birds and then we are given this fact in which Emily saw an animal flying in between two trees. However, it still concludes that there was less than 5% that this animal flying in between two trees was a bird. Shouldn't this raw chance be slightly altered by the fact that it is probably more likely that this is a bird if it is flying? Yes, just like if the Dr. is named Shirley it is probably more likely to be a female.

[jones.mchandler]

I liked Matt's explanation (thanks!) but I actually saw the argument and the answer choices a little bit differently. Can someone see if my thoughts were on the right track?

Thanks!

The Argument Core
Shirley Martin wrote a letter, mentioning that she was a med school professor
+
<1/20 of the professors at such schools are women
→
>19/20 chance that the letter was written by a man

The Flaw: the argument fails to consider other, potentially useful, counter-evidence that could affect the probability of deciphering whether or not this letter was written by a woman or man. Perhaps most men don't write letters but instead compose emails or perhaps the name Shirley makes it more likely that the writer is a woman. In other words, the argument's premise exists in a vacuum; it is saying all else being equal the chances of randomly selecting a female med professor is less than 1/20. However, the conclusion fails to consider that all else may not be equal.

The Answer Choices

(A) This flaw seems very similar to the flaw originally committed in the argument. This answer choice also bases its conclusion on a proportion. However, what made me feel skeptical about this was the actual premise of the argument. For the original argument, the proportion is the main premise. For this argument, concrete evidence (that 1 computer to be used solely for word processing) was the main premise. It seems like the following would be a sufficient correction:


CORRECTION: Since 19 out of 20 home computers are purchased primarily for computer games, this computer sold will almost certainly be used primarily for computer games.

To me, this seems a lot closer because it fails to give any justifiable evidence for believing that this randomly selected computer will be used for computer games. Maybe this computer is being sold to a business professional.

(B) This is basically the same thing as (A). It has the same flaw as the original argument (not taking into account other useful evidence that may affect the chances) but does so in a different way than the original argument. Like (A), if we eliminated the main premise, "Since only 15 manuscripts...last week" and just based our argument on the probability, it seems like it would be right, no?

Hey Walt, I saw the flaws in A and B a little differently. I don't think the flaw quite matched the flaw in the stim (failing to consider other useful info that could influence the chances). It seemed that these flaws just rested on an incorrect usage of averages, where they arguments assume what's happened in the past (bought a home computer, as in A) affects the likelihood that a computer will be purchased for gaming in the future. Maybe the difference is two sides of the same coin, but that's how I differentiated them

[WaltGrace1983]

Hey Walt, I saw the flaws in A and B a little differently. I don't think the flaw quite matched the flaw in the stim (failing to consider other useful info that could influence the chances). It seemed that these flaws just rested on an incorrect usage of averages, where they arguments assume what's happened in the past (bought a home computer, as in A) affects the likelihood that a computer will be purchased for gaming in the future. Maybe the difference is two sides of the same coin, but that's how I differentiated them

You know, I think you are totally right. I am going to edit that response up top.

[DevinD793]

What exactly does 19 to 1 mean?