Critical Reasoning for Beginners

Hello Friends,

Below is the summary of what i have been able to understand of Critical Reasoning (So far). I have compiled my notes from various sources and credit goes to original authors such:
1) Kaplan comprehensive program 2009 and verbal workbook (good and concise)
2) Princeton, crack the GMAT (not too good. just basic)
3) Unknown blogger (https://gmat-cr.blogspot.com/search/labe ... STRATEGIES)
4) Most importantly blogger by name of Mukul Hinge (https://www.mukulhinge.com/CRBasics.html)
5) Tough diagnostic questions and good explanations to answers from https://www.informit.com/articles/articl ... 9&seqNum=6
6) Fundamental as explained by https://www.prepfortests.com/gmat/tutori ... ing/whatis
7) A good walk through presentation
Hope you all you would find this post useful.

Thanks and all the best to all
GS
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Critical Reasoning Basics
1. Logic is a system of reasoning that allows us to arrive at conclusions using available data and critically check the validity of these conclusions.
2. Argument / Stimulus; in critical reasoning we consider group of related propositions. An argument is set of two or more propositions (called premises) in such a way that all but one of them (premises) provide support for the remaining one (conclusion)
3. Line of reasoning; the transition or moment from premises to the conclusion, the logical connection between them, is called line of reasoning.
4. Assumption; the un-stated premises that make or break the conclusion of the argument / stimulus
5. Conclusion; Contains the central idea of the argument.
• Conclusion = Premises + Assumption (the one that links the premises)
• If premise are valid and sufficient, then the conclusion must be true. Conversely if the conclusion is invalid, then
premises must be invalid or in sufficient or both. . . But if premises are invalid the conclusion is not necessarily invalid.
6. Inference; are un-stated partial conclusions that can be drawn from the given premise. They do not contain the central idea, but they lead to/support the central idea.
• An inference can serve as a link in the line of reasoning but is not the same as conclusion. A conclusion
invariably addresses the central idea of the stimulus whereas inference serves only to support the conclusion
• There can be many inferences; such as immediate inference, followed by final inference, before it leads to
conclusion.

Putting the above together; lets see examples

EXAMPLE 1
I ate mango today
I went to school
he is good man
. . . .the above three are just set of statements / premises that have no connection or line of reasoning.

EXAMPLE 2
. . . .unlike in above example in the following statements / premises there are connections:
Jimmy is a doctor (premise)
All doctors go to medical school.(premise)
So jimmy went to medical school (conclusion)

EXAMPLE 3
. . . . lets see an example that highlights; Conclusion v/s inference;
Premise #1: Students who get seven hours of sleep at night tend to be more alert the next day than those who don’t get seven hours of sleep
Premise #2: The ability to get good scores in any competitive exam depends on one’s level of alertness.
• Inference: From the above two we can infer that, “if you are a student (may not be true for others) you are likely to be more alert next morning if you get seven hours of sleep”
• Conclusion: From the above two we can conclude that, “student (may not be true for others) wishing to do well in competitive exams should try and get at least seven hours of sleep on day before the exam)


Important
• Logic can give us a consistent and reliable method of inferentially arriving at a conclusion but cannot guarantee the validity of the statements / premises used in constructing an argument.
• In critical reasoning u have to accept the truth of the stated premises and you only validate the conclusion. That is to say, in critical reasoning A FACT is 100% TRUE; a FACT or as we say a PREMISE can never be strengthened or weakened; only the CONCLUSION can be strengthened/weakened.



Approaching / Solving Critical Reasoning Questions
1 Read the stimulus, little swiftly
2 Read the question & re-read the stimulus, little steadily
3 Identify the conclusion**
4 Separate the evidence from the conclusion
5 Re-arrange the premise and conclusion to get clear line of reasoning
6 Pre-phrase the answer
7 Attack the question
**Yes!! this is the most important step. If you have identified conclusion correctly your half battle is won. You might be wondering that whats so big deal about identifying the conclusion. next time when you practice CR try identifying conclusion first you will see difference; while reading stimulus we tend to believe we have identified the conclusion whereas we have note. . . . identifying conclusion is so very important because, its the conclusion which is verified, strengthen or weakened and not the premises (which are 100% fact and have to be taken as truth)


Remember
• To distinguish between conclusion and evidence ask "what does the author believe" (conclusion) OR "why does the author believe" (Evidence)
• Breaking the arguments into premises / evidence & conclusions is important as our minds naturally want to understand what we are reading, and sometimes we assume connections between the premises and conclusions of an argument that “don’t” exist. By doing this, our minds often make of arguments that don’t.
• Fight your habit to make assumptions regarding arguments and watch out for illogical connections the test wants you to make!
• Don’t assume information unless you see it in the argument.
• Memories what the questions is asking. Before you start attacking the question, identify what is to be done; what is to be destroyed or strengthened or identified (Mumble the reply to yourself & memorise what need to be looked for in answer choices; then you won’t have to re-read the stimulus).
• Think of word “destroy” when strengthening or weakening an argument.
• Don’t get stuck on one answer option (instead read other choices, which will help u eliminate faster); just as in data sufficiency if first statement seems complicated you move on to second one and eliminate the wrong choices, and then come back to the first statements)
• Each of the answers choices will do one of the following;
- It will weaken the argument.
- Or It will strengthen the argument.
- Or It will not affect the argument at all (neutral)
- Or will be out of scope.
• KISS. Keep things short and simple.
• Stick within the scope; strengthen or weaken in context of conclusion not otherwise. Even if the option seems ok ask yourself if it’s in the context of the conclusion. Answer choice has to be the one which has reference in the conclusion.
• Unlike RC, in CR, answer choice with ‘Strong’ wording need not be eliminated, in fact if wording is too qualified (containing words like some, occasionally, or possibly), check whether statement is truly strong enough to affect the argument


Types of questions
1. Identify assumption / strengthen / weaken the conclusion
• If assumption is true, then conclusion has to be true whereas if assumption is invalid conclusion has to be invalid i.e. Assumption can validate / strengthen the argument if true or can invalidate / weaken the argument if false
• While identifying the assumption you need to separate what is relevant from what is crucial to the discussion / argument.
• Avoid answer that re-state the premises
• In Strengthen / weaken questions avoid answer choices that do opposite of what is asked
• ‘EXCEPT’ questions; right answer is that least significantly affects the conclusion

2. Identify the conclusion
• Note: For ‘identify the conclusion’ question, since the conclusion is not in the passage, the answer can’t be restatement of the information given in the passage.
• The conclusion has to be supported by all the evidence in the passage i.e. it should connect / make use of all the premises. And not just link up with just one (of many) premises refer.

3. Deduce the conclusion / get the inference
• No outside information should be added
• If choice needs any additional assumption to work, then its wrong
• Additionally, when question says, “if the information provided in the passage is true” any option that express doubt about the information provided is also out
• In inference questions be vary of answer choices that;
. . . . . Go outside the scope (the right choice should be just a step ahead in direction what can be deduced from the premises, which eventually leads to conclusion)
. . . . . Are too extreme (be wary of words such as never, always, must etc.)

4. Mimic the reasoning Depending on question type you will need to use one of the following 3 METHODS

METHOD 1: Use Venn diagrams

example :1
All vehicles with 4 stroke engine need maintenance after a year.
Your bike is a 4 stroke.
Therefore, your bike will needs maintenance after a year. This conclusion is perfectly fine and can be represented in form of Venn diagram as follow:



example :2
All men are idiots
Tom is an idiot
Therefore Tom is a man; this conclusion is perfectly fine and acceptable in GMAT. But, when we see carefully this same stimulus can be logically valid without being factually correct

B: Set of all idiots
A: Set of all men (contained in B)
C: Tom (can fall outside A) . . . so, you see that TOM could be a man or could not be a man; irrespective for purpose of CR in GMAT, the conclusion 'Tom is a man', is perfectly acceptable

METHOD 2: Use x, y, z to simply questions

METHOD 3: Use logical operators; In questions which involve straight forward negation or conditional analysis

‘If not’ operator denoted by ‘!’
if A then B, if !B then !A

‘And’ operator denoted by ‘&’
If A & B = C
!A => !C
!B=> !C
!A & !B =>!C

‘OR’ denoted by ‘||’
If A ||B = C
If A, !B => C
If B, !A => C
If !A , !B => !C
If A & B => C

5. Resolve the paradox
• Find the missing link that ensures that both /all the premises in the argument stand true.

6. Identify the flaw
• Don’t confuse flaw question with weaken question; in weaken question you are supposed to find the additional information which if true would destroy the argument, whereas in flaw question, you know the evidence doesn’t support the conclusion very well at all, and its up to you to explain why

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