Difference between Sufficient Assumptions and Necessary Assumptions

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laker
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Difference between Sufficient Assumptions and Necessary Assumptions

Postby laker » Mon Sep 04, 2017 6:52 pm

Hey there, could anyone give me an explanation for the difference between sufficient assumptions and necessary assumptions? I seem to be getting these mixed up pretty frequently.

Thanks!

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Platopus
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Re: Difference between Sufficient Assumptions and Necessary Assumptions

Postby Platopus » Mon Sep 04, 2017 6:59 pm

What books are you using to study? If you are still struggling with this (and this is a HUGE part of LSAT), you should be hitting the books again. I'd recommend Powerscore and Manhattan for LR, but I would honestly start with the Powerscore LG bible, as that has a good foundation for wrapping your head around conditional logic. While I'm sure people will explain it here, I'm also certain that these books will give you a more thorough explanation.

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laker
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Re: Difference between Sufficient Assumptions and Necessary Assumptions

Postby laker » Mon Sep 04, 2017 7:08 pm

I'm working through the LSAT Trainer right now and I just got to the chapter on sufficient/necessary assumptions. I definitely understand conditional logic, I'm just a little confused on applying it to the assumptions.

My understanding of it:

A sufficient assumption asks you to find an answer choice that, if assumed, would be sufficient to bring about the conclusion.. so Answer choice (true) -> conclusion (correct).

A necessary assumption asks you to find an answer choice that needs to be assumed in order for the argument to work.. so Argument (valid) -> answer choice (true).

Is my understanding correct? Thanks

mmart207
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Re: Difference between Sufficient Assumptions and Necessary Assumptions

Postby mmart207 » Mon Sep 04, 2017 8:13 pm

laker wrote:I'm working through the LSAT Trainer right now and I just got to the chapter on sufficient/necessary assumptions. I definitely understand conditional logic, I'm just a little confused on applying it to the assumptions.

My understanding of it:

A sufficient assumption asks you to find an answer choice that, if assumed, would be sufficient to bring about the conclusion.. so Answer choice (true) -> conclusion (correct).

A necessary assumption asks you to find an answer choice that needs to be assumed in order for the argument to work.. so Argument (valid) -> answer choice (true).

Is my understanding correct? Thanks


Think of it as Necessary assumptions giving you half of the arrow that leads to the conclusion being properly drawn, while sufficient assumptions provide you with the entire arrow.

RSolano
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Re: Difference between Sufficient Assumptions and Necessary Assumptions

Postby RSolano » Tue Sep 05, 2017 7:51 am

Sufficient completely bridges the gap or hole in the argument allowing the conclusion to be fully drawn. Pretty easy to predict or pre phrase

Necessary conditions are just anything that has to be assumed for the argument to be valid. If you negate the correct answer for one of these questions it will destroy the argument completely. They're hard to predict or pre phrase because there are so many possibilities down to really obvious stuff.

mmart207
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Re: Difference between Sufficient Assumptions and Necessary Assumptions

Postby mmart207 » Tue Sep 05, 2017 1:52 pm

RSolano wrote:Sufficient completely bridges the gap or hole in the argument allowing the conclusion to be fully drawn. Pretty easy to predict or pre phrase

Necessary conditions are just anything that has to be assumed for the argument to be valid. If you negate the correct answer for one of these questions it will destroy the argument completely. They're hard to predict or pre phrase because there are so many possibilities down to really obvious stuff.


I wouldn't say they're hard to predict at all. I find myself predicting the correct answer before I even look at the choices.

RSolano
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Re: Difference between Sufficient Assumptions and Necessary Assumptions

Postby RSolano » Thu Sep 07, 2017 1:09 am

mmart207 wrote:
RSolano wrote:Sufficient completely bridges the gap or hole in the argument allowing the conclusion to be fully drawn. Pretty easy to predict or pre phrase

Necessary conditions are just anything that has to be assumed for the argument to be valid. If you negate the correct answer for one of these questions it will destroy the argument completely. They're hard to predict or pre phrase because there are so many possibilities down to really obvious stuff.


I wouldn't say they're hard to predict at all. I find myself predicting the correct answer before I even look at the choices.


True I guess I should say don't go in with a rigid fixed expectation because sometimes a much broader unexpected right answer can get accidentally eliminated that way.




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