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Logical Reasoning Question
Posted: Wed May 23, 2012 12:52 pm
by Bilqis
Hello everyone
Could somebody please explain to me this logical relationship:
If no J then S
Does that mean if J is there that S cannot be there?
Thank you
Re: Logical Reasoning Question
Posted: Wed May 23, 2012 1:08 pm
by mmm2602
No.
"If (not J) then S" implies "if (not S) then J", not "If J then (not S)"
Re: Logical Reasoning Question
Posted: Wed May 23, 2012 1:37 pm
by Bilqis
Thanks a lot, that was helpful!
Re: Logical Reasoning Question
Posted: Wed May 23, 2012 1:42 pm
by Bilqis
Okay this is a tough one, could you or anybody tell me why the answer to the following is A?
If there are any inspired musical performances in the concert, the audience will be treated to a good show. But there will not be a good show unless there are sophisticated listeners in the audience, and to be a sophisticated listener one must understand one's musical roots.
A) If there are no sophisticated listeners in the audience, then there will be no inspired musical performances in the concert
Re: Logical Reasoning Question
Posted: Wed May 23, 2012 1:44 pm
by Bilqis
tfleming09 wrote:This rule is a difficult concept for a lot of people. It's weird to think the absence of something triggers the presence of something else.
The rule is: if no J, then S
Diagrammed as such:
J -----> S
via the contrapositive:
S -----> J
The presence of the necessary condition does not have to preclude the sufficient condition. Or, simply, you can have one, the other, or both. They can just never BOTH be absent
So one of them always has to be there. Think of it this way: it's like two parents share responsibility to pick their kids up from school. Someone always has to be there, or their kid has no way to get home. There are three possibilities:
Mom picks kids up
Dad picks kids up
Mom and dad pick kids up together
Hope this helps. It's a weird rule at first.
Thank you so much, very helpful!
Re: Logical Reasoning Question
Posted: Wed May 23, 2012 6:33 pm
by btowncane
Bilqis wrote:Okay this is a tough one, could you or anybody tell me why the answer to the following is A?
If there are any inspired musical performances in the concert, the audience will be treated to a good show. But there will not be a good show unless there are sophisticated listeners in the audience, and to be a sophisticated listener one must understand one's musical roots.
A) If there are no sophisticated listeners in the audience, then there will be no inspired musical performances in the concert
Basically you can break that stem down into three conditional statements where:
IMP = Inspired musical performance
GS = Good show
SL = Sophisticated listeners
Also, keep in mind that "unless" changes the affected condition to "if not".
1. IMP → GS
Contrapositive (CP): ~GS → ~IMP
2. ~SL → ~GS
CP: GS → SL
3. SL → UMR
CP: ~UMR → ~SL
Then combine the relationships starting with not sophisticated listeners and you get:
~SL → ~GS → ~IMP
Which is a longer way of saying:
~SL → ~IMP
Hope this helps.
Re: Logical Reasoning Question
Posted: Thu May 24, 2012 12:54 pm
by Bilqis
Btwocane
That was very helpful, thank you
Re: Logical Reasoning Question
Posted: Thu May 24, 2012 1:19 pm
by LoveLife89
It basically means it has to be one or the other. It could be both but at least one of them has to always be included
Re: Logical Reasoning Question
Posted: Fri May 25, 2012 1:53 pm
by bp shinners
Negating the sufficient condition creates an "at least one" relationship. That's the most straightforward way I have found to explain this concept.
Re: Logical Reasoning Question
Posted: Mon May 28, 2012 10:35 pm
by Bilqis
Thank you all for replying! It's clearer to me now