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# LOGICAL REASONING

By Alexander Smith,2014-08-29 10:20
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LOGICAL REASONING

Logical Reasoning Bible

解 题 思 路 整 理

IPrimary Objectives:

1.Determine whether the stimulus contains an argument or if it is only a set of

factual statements;

2.If the stimulus contains an argument, identify the conclusion of the argument; If

the stimulus contains a fact set, examine each fact;

3.If the stimulus contains an argument, determine whether the argument is strong or

weak;

4.Read closely and know precisely what the author said. Do not generalize;

5.Carefully read and identify the question stem; Do not assume that certain words

are automatically associated with certain question types;

6.Prephrase; After reading the question stem, take a moment to mentally formulate

8.Separate the answer choice into contenders and losers; After completing this

process, review the contenders and decide which is the correct one;

argument.

IIBasics of Logical Reasoning

Premise IndicatorsCounter-Premise IndicatorsConclusion Indicatorsbecause, since, for, for But, yet however, on the thus, therefore, hence,

example, for the reason that, other hand, admittedly, in consequently, as a result, so,

in that, given that, as contrast, although, even accordingly, clearly, must

indicated by, due to, owing though, still, whereas, in be that, shows that,

to, this can be seen from, spite of, despite, after allconclude that, follows that,

we know this by, for this reason,

furthermore, moreover,

more, after all

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Quantity IndicatorsProbability Indicators

all, every, most, many, some, several, few, Must, will, always, not always, probably, sole, only, not all, nonelikely, would, not necessarily, could, rarely,

never

I题型

Family #1Must Be or Prove Family

1.Must Be True Questions

Fact TestThe correct answer to a Must Be True

question can always be proven by referring

to the facts stated in the stimulus.

You can often predict the occurrence of

Must Bu True questions because the

stimulus of most Must Be True questions

portion of the stimulus in different

terms.

from combining 2 or more

New Info;

Shell Game;

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2.Main Point Questions

Many Main Point problems Incorrect Answer Types:Main Point---Fill in the feature a structure that Blank Questions

a. Answers that are true but places the conclusion either

do not encapsulate the The blank is always at the at the beginning or in the

author’s point;end of the stimulus. There is middle of the stimulus.

a conclusion indicator at the

b. Answers that repeat start of the sentence to help

premises of the argument.you recognized that are

being asked to fill in the

conclusion of the argument.3.Point at Issue

Incorrect Answers in Point a. Ethical versus Factual Situations;at Issue Questions

b. Dual Agreement or Dual Disagreement;

c. The View of 1 Speaker is Unknown.The Agree/Disagree TestThe correct answer must produce responses where one

speaker would say “I agree, the statement is correct” and

the other speaker would say “I disagree, the statement is

incorrect”. If those two responses are not produced, then

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4.Method of Reasoning

Method of Reasoning Questions TypesThe stimulus for a Method of Reasoning

question will contain an argument, and the argument can contain either valid or invalid reasoning.

You must watch for the presence of the premise and conclusion indicators.

Use Fact Test to eliminate answers. If an answer choice describes an event that did not occur in the stimulus, then that answer is incorrect.

Several types of incorrect questions:

Half Right, Half Wrong;

Method of Reasoning—Argument Part Method—AP questions often feature 2

Questionconclusions—a main conclusion and

subsidiary conclusion—where the main conclusion is typically placed in the first or second sentence and the last sentence contains the subsidiary conclusion.

Trick: the test makers in Method—AP is to create wrong answers that describe parts of the argument other than the part named in the question stem.

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5.Flaw Questions

Common Errors of Reasoning Explained

a. Uncertain Use of a Term or Concepti. Appeal Fallacies

Appeal to authority;

Appeal to Popular Opinion/Appeal

to Numbers;

Appeal to Emotion.

b. Source Argumentj. Survey Errors

ad hominem, or attack the person (or Survey uses a biased sample;source)

Survey questions are improperly

Focusing on the motives of the constructed;

source;

Respondents to the survey give

Focusing on the actions of the inaccurate responses.

source.

c. Circular Reasoningk. Exceptional Case/Overgeneralizationd. Errors of Conditional Reasoningl. Errors of Compositions and Division

Mistaken Negation;以偏全或以全偏概概

Mistaken Reversal;

Confuse a necessary condition

for a sufficient condition;

Confuse a sufficient condition

with a required condition.

If you identify a stimulus with

conditional reasoning and are asked a Flaw

question, you can quickly scan the answers

for the one answer that contains

“Sufficient”, “Necessary” or both.

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e. Mistaken Cause and Effectm. False Analogy

Assuming a causal relationship

on the basis of the sequence of

events;

Assuming a causal relationship

when only a correlation exists;

Failure to consider an alternate

cause for the effect, or an

alternate cause for both the cause

and the effect;

Failure to consider that the events

may be reversed.

If you identify a stimulus with causal

reasoning and are asked a Flaw question,

quickly scan the answers for one that

contains “Cause”, “Effect” or both.

f. Straw Mann. False Dilemma

Ignore the actual statements made by the

opposing speaker and instead distorts and

refashions the argument.

g. General Lack of Relevant Evidence of o. Errors in the Use of Evidencethe Conclusion

Lack of evidence for a position is

taken to prove that position is false;

Lack of evidence against a position

is taken to prove that position is

true.

Some evidence against a position is

taken to prove that position is false;

Some evidence for a position is

taken to prove that position is true.h. Internal Contradictionp. time shift errors

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q. Numbers and Percentages Errors.

Author improperly equates a percentage

with a definite quantity, or when an author

uses quantity info to make a judgment

about the percentage represented by that

quantity.

6.Parallel Questions

The question stem for any Parallel question reveals whether the stimulus contains valid or

invalid reasoning. If the question stem mentions a flaw, then the reasoning is invalid. If

the question stem does not mention a flaw, then the reasoning is valid.The following elements do a. Topic of the stimulus;

not need to be paralleled:

b. The order of the presentation of the premises and

conclusions in the stimulus.

You must parallel all of a. The Method of Reasoning;

these elements:

b. The Validity of the Argument;

c. The Conclusion;

d. The Premises.

If all else fails,Create a short statement that summarizes the “action” in

the argument. Then take the abstraction and compare it to

each argument.

Family #2Help Family

7.Strengthen Questions

To effectively strengthen 3 Incorrect Answer TrapsTo strengthen a Cause and

argumentsEffect relationship

Identify the conclusion;Eliminate any alternate Opposite answers;

causes;

Show that when the cause

Look for weakness or holes occurs, the effect occurs;Out of scope in the argument.

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does not occur, the effect

does not occur;

Eliminate the possibility

that the stated relationship is

reversed;

Show that the data used to

make the causal statement is

accurate, or eliminate

possible problems with the

data.

8.Justify Questions

Justify FormulaThe following rules apply:

Premise + Answer Choice = Conclusiona. Any “New” element in the conclusion

will appear in the correct answer;

b. Elements that are common to the

conclusion and at least 1 premise, or to 2

premises, normally do not appear in the

c. Elements that appear in the premises but

not the conclusion normally appear in

9.Assumption Questions

The relationship between the conclusion and the assumption can be described as:

Conclusion Assumption ValidTrue

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Supporter/Defender Assumption Model

Supporter Assumption: These assumptions link together new or rogue elements in the stimulus or fill logical gaps in the argument.

Defender Assumption: These assumptions statements that eliminate ideas or assertions that would undermine the conclusion.

If there is no obvious weakness in the argument and you are faced with an Assumption question, expect to see a Defender answer choice.

Assumption Negation Technique:

a. logically negate the answer choices under consideration;

b. the negated answer choice that attacks the argument will be the correct answer.3 Quirks of Assumption Question Answer Choice:

a. Watch of answers starting with the phase “at lease one” or “at least some”;b. Avoid answers that claim an idea was the most important consideration for the author;c. Watch for the use of “not” or negatives in assumption answer choices.Assumptions and Conditionality:

a. If conditional statements are linked together in the argument, the correct answer choice for an Assumption question will typically supply a missing link in the chain;b. If no conditional chains are present and only a conditional conclusion exists, the correct answer will usually deny scenarios where the sufficient condition occurs and the necessary does not, or it works as a Defender.

Assumption and Causality: ?解题思路Strengthen Causality题似?

a. Eliminate any alternate causes;

b. Show that when the cause occurs, the effect occurs;

c. Show that when the cause does not occur, the effect does not occur;d. Eliminate the possibility that the stated relationship is reversed;e. Show that the data used to make the causal statement is accurate, or eliminate possible problems with the data.

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The correct answer will The following types of Note: You must address the allow 2 sides to be factually answers are incorrect:facts of the situation. Many correct. answers will try to lure you

explain only 1 side with reasonable solutions

that do not quite meet the of the paradox;

b. Similarities and are incorrect.

differences.

Family #3Hurt Family

11.Weaken Questions

Fundamental RulesCommon Weakening 3 Incorrect Answer Simple Rule for

ScenarioTrapsweakening a

conditional

reasoninga. The stimulus will To weaken a Incomplete Opposite

conclusion, attack b. Focus on the the necessary Improper Shell game

showing that the c. The info in the necessary condition Qualified Out of stimulus is suspect. does not need to conclusion.scope There are often occur in order for answers.reasoning errors the sufficient present, and you condition to occur.must read the

argument very

carefully;

d. Weak questions

often yield strong

prephrases;