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Author Topic: logical reasoning help  (Read 863 times)

Lindbergh

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Re: logical reasoning help
« Reply #10 on: October 09, 2007, 02:18:33 AM »
can anybody help me diagram this please?

"no politician is censured unless he or she is known to be involved in a serious scandal"

thanks  :)

It's from Preptest 39 (Dec 02), Sec 2, #6

Censored  -------->  Involved Scandal

thanks ubiquitous.

that's what got me confused. i diagrammed it exactly like you did.

the correct answer was A) the politicians cannot avoid censure (paraphrased)

which is basically the contrapositive of what you stated.

the stimulus was: a politician can neither be reelected nor avoid censure if he/she is involved in any scandals. these politicians have just been shown to be involved in a scandal. (paraphrased)

i can't see why C is incorrect because its the contrapositive of A.

can anybody tell me why C is incorrect?  ???

Because it is the incorrect answer.

You and Ubiquitous law are both wrong in your diagrams.

The correct diagram is: Involved in Scandal > Censured

Not being censured is not sufficient to guarantee that a politician was not involved in a scandal.


Last time I checked, "unless" introduces the necessary condition, while the sufficient condition becomes negated (Testmasters rule and Logical Reasoning Bible).

"no politician is censured unless he or she is known to be involved in a serious scandal"

"unless"  makes "involved in scandal" necessary condition, while negation of  "censured" becomes the sufficient condition. The "no" at the beginning of the sentence negates "involved in scandal". Thus..............   Censored -------> Involved Scandal or    Involved Scandal -----> Censored (Contrapositive).

This is my reasoning from reading OP's post.



"unless introduces the necessary condition"

So, as noted, Scandal will be the 2nd term in the conditional statement:  X -> Scandal.

Sufficient condition (not censured) becomes negated for sufficient (first) condition = Censured -> Scandal.

Ubiquitous law

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Re: logical reasoning help
« Reply #11 on: October 09, 2007, 02:29:19 AM »
can anybody help me diagram this please?

"no politician is censured unless he or she is known to be involved in a serious scandal"

thanks  :)

It's from Preptest 39 (Dec 02), Sec 2, #6

Censored  -------->  Involved Scandal

thanks ubiquitous.

that's what got me confused. i diagrammed it exactly like you did.

the correct answer was A) the politicians cannot avoid censure (paraphrased)

which is basically the contrapositive of what you stated.

the stimulus was: a politician can neither be reelected nor avoid censure if he/she is involved in any scandals. these politicians have just been shown to be involved in a scandal. (paraphrased)

i can't see why C is incorrect because its the contrapositive of A.

can anybody tell me why C is incorrect?  ???

Because it is the incorrect answer.

You and Ubiquitous law are both wrong in your diagrams.

The correct diagram is: Involved in Scandal > Censured

Not being censured is not sufficient to guarantee that a politician was not involved in a scandal.


Last time I checked, "unless" introduces the necessary condition, while the sufficient condition becomes negated (Testmasters rule and Logical Reasoning Bible).

"no politician is censured unless he or she is known to be involved in a serious scandal"

"unless"  makes "involved in scandal" necessary condition, while negation of  "censured" becomes the sufficient condition. The "no" at the beginning of the sentence negates "involved in scandal". Thus..............   Censored -------> Involved Scandal or    Involved Scandal -----> Censored (Contrapositive).

This is my reasoning from reading OP's post.



"unless introduces the necessary condition"

So, as noted, Scandal will be the 2nd term in the conditional statement:  X -> Scandal.

Sufficient condition (not censured) becomes negated for sufficient (first) condition = Censured -> Scandal.

Ok, I understand that "unless" is introducing the necessary, but what about the "no" in the sentence. Doesn't the "no" introduce the sufficient, and negate the necessary. This is why I negated Scandal in the first place.

The "no" intros censure as sufficient, and "unless" intros scandal as necessary. "no" negates scandal at the same time, while "unless" negates censure at the same time.

Is my reasoning wrong because I misunderstood the meaning of "no" in the sentence?
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killblues

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Re: logical reasoning help
« Reply #12 on: October 09, 2007, 02:35:35 AM »
Take the part after "unless" as necessary, the negate the other part as sufficient.

Censured --> scandal

geegorie

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Re: logical reasoning help
« Reply #13 on: October 09, 2007, 06:05:53 AM »
This is the trick that I use. With an "unless" whatever I put as the sufficient condition I negate.

For example, censured --> serious scandal and contra positive of that is no serious scandal --> not censured.

Just remember with unless or any other negate necessary conditional markers, whatever you choose to place as the sufficient condition must be negated. Hope that helps. And before anyone points out that I am wrong, from my understanding and experience it doesn't matter whether you use the contra positive or the original statement first. You can make the proper inference from either or.

Correct me if I am wrong.   
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