PT 51 section 3- diabolical LR section

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walterwhite

Posts: 178
Joined: Thu Jul 18, 2013 8:31 pm

PT 51 section 3- diabolical LR section

I thought the end of this section, from about question 18-23 was very difficult.

Specifically question 19 was impossible. Are you supposed to take the contrapositive of each of the conditionals statements in the stimulus? I did that and got choice C, instead of D.

I'm also struggling to understand 20 (another question with conditional statements).

JWP1022

Posts: 269
Joined: Mon Dec 03, 2012 10:15 pm

Re: PT 51 section 3- diabolical LR section

You are right, questions 18-23 are very difficult. I got 21 wrong when I took this PT, I believe. I'll cover the two questions you asked specifically about.

PT 51, S3, 19

There is a lot of conditional logic in this stimulus. We are told (paraphrased) that "if archaic spellings occur infrequently and do not intefere with the reader's comprehension, then they should be preserved." This diagrams to:

Occur Infrequently + ~Interfere with reader's comprehension --> Preserve

We are then told that "if archaic spellings occur frequently, then it is okay to modernize while adding an explanation." This diagrams to:

Occur Frequently --> Modernize (and add explanation!)

The stimulus then adds that obvious typographical errors can be corrected without explanation. This doesn't really matter to figuring out the answer to this question, but can be diagrammed to:

Obvious Typographical Errors --> Modernize/Correct without Explanation

Now, this is a "Must Be True" question. Given the facts and relationships presented in the stimulus, we have to figure out which answer follows logically and can never be false.

The first things you should notice about the conditional logic in this question is that it doesn't really set off a chain. These relationships don't really "interact" with one another, rather they just present courses of action for a given situation. Do the spellings occur frequently? Great, then modernize them with an explanation. Do they occur infrequently and not interfere with reader comprehension? Leave em be! In this way, this is almost like a "principle apply" question, where you are given a set of rules and have to figure out what course of action fits those rules. With that in mind, let's take a look at the answers:

A) This answer is much too broad. We don't really know the definition of "frequently" as it appears in the stimulus, but it might be safe to say that a word appearing once does not constitute appearing "frequently". Cross it off.

B) There is no support for this based on the rules presented in the stimulus. If we modernize a word that appears frequently, we have to provide an explanation. If we decide to modernize direct quotations that, say, interfere with reader comprehension, we have no idea whether or not we cmuist correct it based on the stimulus. Be careful with this one as this AC says "modernize" and not "correct." If it had said "correct a word without explanation" it would be a correct answer based on teh final choice of the stimulus.

C) This is a flaw. We cannot infer this from the conditional relationships presented. We are told that NOT interfering with RC AND infrequent occurrence are SUFFICIENT for preserving the spellings. We cannot then say that interfering with RC is sufficient for not preserving/modernizing the statements.

D) Eureka! This is what we're looking for. This AC is a direct application of the second conditional relationship, although it is a little bit obscured by the addition of "interfering with reader comprehension." In the second relationship, the ONLY thing that you need to justify modernizing the words is that they appear FREQUENTLY. If the spellings appear frequently, you can modernize them (with an explanation). This choice says exactly that; whether or not they interfere with reader comprehension is irrelevant.

E) There is no support for this in the stimulus. The stimulus gives us no guidance for what we should do when we slectively correct spellings/punctuation.

PT 51, S3, 20

This is a Sufficient Assumption question. This means that we are looking to build a "bridge" to the conclusion by filling in an assumption in the argument.

We are told several things in the stimulus:

1. Whoever murdered Jansen was UNDOUBTEDLY in Jansen's office on the day of the murder.
2. Both Samantha and Herbert were in Jansen's office.

We are then given two conditional relationships:

3. If Herbert had committed the murder, the police would have either found his finger or footprints.

Herbert committed the murder --> Fingerprints OR Footprints
CP: ~Fingerprints AND ~Footprints --> ~Herbert committed the murder

4. If Samantha was the murderer, she would have left neither fingerprints nor footprints. This is a tricky one to diagram, because the necessary condition is actually an AND statement instead of an OR statement.

Samantha committed the murder --> ~Fingerprints AND ~Footprints
CP: Fingerprints OR Footprints --> ~Samantha committed the murder

5. There were fingerprints but no footprints.

6. The fingerprints were not Herberts, so he is not the killer, since we know if he left neither fingerprints nor footprints that he can't be the killer.

CONCLUSION: Samantha must be the killer.

At first glance, it looks like we need to find a way to prove that Samantha is the killer based on the fingerprints/footprints (or lack thereof) mentioned in the stimulus. But wait a second, there's a catch. In the Samantha-relevant conditional, a lack of fingerprints and footprints is a NECESSARY condition for Samantha being the killer. Establishing that Samantha left neither fingerprints nor footprints is necessary to proving she is the killer, but it DOES NOT GUARANTEE THAT CONCLUSION. Remember, we are looking for a sufficient assumption. This is why E is a tricky answer choice, but you are wiser than this!

Look back at the beginning of the stimulus. We are told that the killer was undoubtedly in Jansen's office. We must take this as true based on the stimulus. Now look at answer choice C. We have already established conclusively that Herbert is not the killer. If we combine this knowledge with the knowledge that the killer MUST HAVE been in the office, then we know that this answer choice would fill our gap.

The killer was definitely in the office + Herbert is NOT the killer AND (Herbert and Samantha were the only people in the office) --> Samantha must have been the killer.

Definitely tough questions.

Make sense?

walterwhite

Posts: 178
Joined: Thu Jul 18, 2013 8:31 pm

Re: PT 51 section 3- diabolical LR section

thanks for the detailed response. I think I was tripped up because I immediately tried to take the contrapositive of all the conditional statements in both questions. I'm a little surprised neither correct answer relied on a contrapositive

JWP1022

Posts: 269
Joined: Mon Dec 03, 2012 10:15 pm

Re: PT 51 section 3- diabolical LR section

walterwhite wrote:thanks for the detailed response. I think I was tripped up because I immediately tried to take the contrapositive of all the conditional statements in both questions. I'm a little surprised neither correct answer relied on a contrapositive

Keep in your mind -- especially at later portions of LR sections -- that in many cases LSAC might include a heavy amount of conditional phrasing in the stimulus to distract you from the real path to the answer. In both cases here, the conditional phrasing was definitely relevant, but not in a way that you would expect.

Jeffort

Posts: 1888
Joined: Wed Jun 18, 2008 4:43 pm

Re: PT 51 section 3- diabolical LR section

JWP1022 wrote:
walterwhite wrote:thanks for the detailed response. I think I was tripped up because I immediately tried to take the contrapositive of all the conditional statements in both questions. I'm a little surprised neither correct answer relied on a contrapositive

Keep in your mind -- especially at later portions of LR sections -- that in many cases LSAC might include a heavy amount of conditional phrasing in the stimulus to distract you from the real path to the answer. In both cases here, the conditional phrasing was definitely relevant, but not in a way that you would expect.

Initial strategy decisions can sometimes be difficult with questions like this where the stimulus contains multiple conditional statements, especially when they are long winded conditions and/or have compound conditions.

The first decision to make is diagram or not diagram? It is important because diagramming can sometimes be time consuming and confusing. When I see multiple conditionals, especially for a MBT/most strongly supported question, before deciding to diagram I first ID the individual conditionals (and usually circle or underline the conditional indicator words in each, "If" in this case) and compare them to see if there are any common/overlapping conditions that appear in more than one of the conditionals.

This is a crucial factor in determining whether investing time in diagramming all the statements out is going to be worth the investment of time. If there is at least one overlapping condition that allows conditionals to be linked/chained together, it is highly likely that the correct answer will be about the connection(s) and the valid inference(s) it generates. So you then put together the diagrams to see the connections and evaluate the answer choices with the diagram.

If there are no connections, like in this case, or no obvious connections, it's probably not going to be worth the time to diagram them out, at least not for connection purposes, since they are just independent conditionals. In this case, just circle the indicator words (IF) so you can quickly find and re-read the conditions as checking answers. Then read the answer choices focusing mainly on looking for ones that conclude as true one of the necessary conditions or else the negated form of one of the sufficient conditions (contrapositive) since those are the only things you can validly conclude by applying the conditionals. Find the one that correctly applies one of the conditionals. It's really just a brute force approach you have to do but refined so that you only focus on what is important and don't waste time doing things that turn out to be unhelpful. The way you refine the information for processing in cases like this is simply identifying the necessary conditions from the statements, looking for those being concluded in answer choices, if no luck then look for answers concluding the negation of one of the sufficient conditions for contrapositive application. You can sort through the answer choices much faster when only looking for those two things.

People sometimes find it helpful to diagram multiple conditionals even when they don't overlap just to keep them straight and in simplified form for memory purposes when analyzing answer choices. I sometimes do that when I think it would make it easier to remember and apply the conditions to the answer choices from diagrams than from the original text but wouldn't with this problem because it could end up making the question harder. When the conditionals have long wordy conditions it can be difficult to come up with clear abbreviations you understand when reading the answers and trying to apply them. The situations where I usually do diagram even when there are no connecting conditions (and in instances of just one conditional in the stimulus) is when the conditional is phrased in a less than straightforward way such as with the word unless or without. I like to have the straight up A ---> B If then form written out with the conditions in the correct left to right order when the original text has them presented in another order and/or it includes a negated term with unless.

I don't diagram when I notice that I'm going to have to put extra effort into making the diagrams understandable and/or going to have to re-read the text again anyway to remember what the abbreviations mean while evaluating answer choices. If I'm going to have to re-read the text to know what the abbrvs mean to use the diagrams while analyzing answers, then making them in the first place was a waste of time. Diagrams are meant to simplify the analysis, not make it more difficult. If you start diagramming and realize you are struggling with it due to trouble making good abbreviations you will remember or some other reason, ditch the idea and just circle/underline the conditionals in the stimulus and make sure you properly understand the suff/necc relationship with the elements (which is suff, which is necc).

As for contrapositives, you just have to be on the look out for answer choices that apply the cp as well as ones that apply the original form of the condition because there is no way to anticipate which way the correct answer will apply a conditional. Sometimes the CR is a contrapositive, sometimes it is not, so you just have to be on the lookout for either method of application.

When first reading a stimulus with several conditionals, wait until you've read the whole thing before deciding whether to diagram or not is the main moral to the story since it can sometimes we time wasting. I use presence or absence of common/linking conditions as the main diagram or not deciding factor along with how easily the conditions can be abbreviated without confusion.

If there are multiple conditionals with formal logic stuff going on (quantifiers All, some, most, none) I'm going to diagram some of it for sure.

If it is a sufficient assumption question and there is a conditional anywhere in the question I always diagram and religiously look out for contrapositive use since those sneaky LSAC question writers love to require use of a contrapositive somewhere in the process of solving many of this type.