#19 - The recent concert was probably not properly promoted

[Dave Killoran]

The reasoning why C is correct is confusing to me.

I diagrammed 19 this way:
Premise: -SO —> PP
Premise: -SO
Conclusion: PP

This is valid inference.

I diagrammed answer C as:
Premise: PR —> -N
Premise: N
Conclusion: -PR

This is also a valid inference the only difference is this conclusion is based on the contrapositive of premise 1, with the contrapositive being:
N —> -PR

My issue is that the conclusion in the question stem is not based off the contrapositive of premise 1; it’s basically a restatement of the premise. I know that Dave above said if we had originally diagrammed the stem as
-PP —> SO (with the contrapositive being
-SO —> PP) then the conclusion in that scenario would be based off the contrapositive as well. However, given the unless equation that is not the way that I would originally diagram the stem. The unless equation tells me to diagram the conditional statement the way I originally did (-SO —> PP) How then would I be able to confidently say that C is the correct answer if answer C is technically based off of the contrapositive of premise 1 in that scenario and the scenario in the question stem is not.

Hi AlexisJay,

Good question! Two things to consider:

1. Remember that a statement and its contrapositive are functionally identical; they are in fact two separate ways of stating the exact same thing. So, in logic and by LSAC they are considered identical. Thus, no matter that starting point, you'd have similar, valid logic.

2. Diagramming, and the order we choose to represent the conditions, is actually our choice as test takers. For example, we talk in our books and courses about how "unless" statements can be diagrammed using the Unless Equation, or they can also be diagrammed by substituting "if not" for unless. We prefer the former method because it produces a diagram that is usually devoid of negatives. But you can do it the other way, and if so, you get a "different looking" diagram:

• Statement: Carl won't go to the store unless Priyanka goes with him:
  
  Unless Equation: C P
  
  "If not" substitution: P C

Those two are the contrapositives of each other, so they are identical, but note how the human choice I made of diagramming resulted in different "initial" diagrams. That's arbitrary, and this is why statements and their CPs can be substituted freely with no logical impact. That idea applies here, and thus the "distinction" you note isn't a true logical distinction to the test makers.

Good eye though, and hopefully this helps explain why it's not an issue. Thanks!

[T.B.Justin]

I parsed this stimulus as follows (I think its accurate):

Because the concert did not sell out and since if it did not sell out, it was poorly promoted, therefore the concert was poorly promoted.

[Adam Tyson]

Looks right to me, T.B.!

Looking back through this thread, there are two aspects that we have mostly ignored, and those are the element of probability and that of expert opinion. We have focused instead on using conditional reasoning. That's fine, since it works here, but the reason it works is because the authors were kind enough to carry over both of those elements into every answer choice. All of them have an element of probability, and all of them have some degree of expert opinion. If an answer was missing one of those elements - if, for example, an answer choice had concluded that something MUST happen - then that answer would no longer be parallel to the stimulus, and we would reject it for that reason and not because of anything to do with conditional reasoning.

Answer D stands out to me for that reason - we never were given any reason to believe the builder. Is he "quite knowledgeable" about these things? I think I would trash that answer with no need to consider whether the argument was based on a contrapositive or a restatement.

So, if I were to break this argument down and be a little bit fussier about it, I would do it this way:

Premise: Wells says Sell Out Poorly Promote
Premise: Wells knows what he's talking about
Premise: Sell Out
Conclusion Probably Poorly Promoted

Answer C hits all the key points:

Premise: Neighbor says Properly Repaired Noticeable
Premise Neighbor knows what he's talking about
Premise: Noticeable
Conclusion: Probably Properly Repaired

As discussed elsewhere in this thread, the restatement in the stimulus and the contrapositive in the correct answer are logically identical, so that' not a reason to reject the answer.

It wasn't essential here, but we usually need to be careful in these Parallel Reasoning questions to track all the elements, and it's a good habit to do so every time.

[Coleman]

I don't understand why "poorly promoted" should be equated with "not properly promoted." For me, being poor and not proper sounds like two different things. My last contenders were A and C, and I ended up choosing A since the original passage suddenly changes its conclusion for "probably not properly promoted" from "poorly promoted" while answer choice (A) did the same - it was supposed to conclude "surgery was not performed by a highly-skilled surgeon" but instead said, "not properly performed."

I thought it would make more sense if the passage rather concluded "poorly promoted" rather than "not properly promoted."

Can you give any suggestion about why poor and improper should be understood in the same context?

[Adam Tyson]

To say that something is poorly done is a pretty good indication that it wasn't done properly, Coleman. The two terms are not identical in meaning, but evidence of one can still support a conclusion about the other.

My first problem with answer A is that the expert in that answer wasn't certain, the way the expert in the stimulus was, but only claimed something was probable. That mismatch is a big problem if we are looking to match all the key elements. The second problem is that the author shifted from a claim about the skill of the surgeon to a conclusion about how well the surgeon performed. That's a much bigger leap than the one you were concerned about, from "poorly promoted" to "not properly promoted." Answer A would have been better (but still not good enough, in my opinion) if the conclusion had been "it probably was not performed by a skilled surgeon."