Supplementary Logical Reasoning 1: Q38

[rowdy]

Please help!

I diagrammed this problem as:

MOST P. Gen GP
SOME P. SC GP
ALL GP GL

I noticed it was a MBT question stem so I immediately went to work finding the contrapositive, and then ran into trouble trying to figure out where to diagram the MOST and SOME details.

I noticed that A seemed to be a mistaken reversal. I wasn't quite sure the exact brand of mistake C and D were making but, they both seemed to be incorrectly reversing without negating anything. I chose E through process of elimination though it did not feel right either.

My first question is whether or not this is the kind of problem I should be diagramming at all? I have noticed that I see a lot of conditional reasoning indicators in stimuli, but often can arrive at an answer (or am led to the right answer after choosing an incorrect answer and examining explanations) without using conditional reasoning diagramming.

How am I supposed to differentiate between a question with indicators for which I am to use Conditional Reasoning diagramming to answer and one where I am not?

Finally, if this is a question utilizing conditional reasoning, how should I have come to D as the right answer.

Sorry for the extensive prompt, but this is something that has given me a fair amount of trouble.

Cheers,

Rowdy

[Clay Cooper]

Hi Rowdy,

Thanks for your questions. I'll try to take them in order. Also, check out this discussion, from our CEO Dave Killoran, the author of the LSAT Bibles:

lsat/viewtopic.php?t=11481

I think his discussion does a great job of dealing with the reasoning present in this question (pretty sure he actually invented conditional reasoning); so I will answer your other questions.

Should you be diagramming this question? and the related question: how do you know when you should and shouldn't diagram a question that contains conditional reasoning?

Basically, I would say that you should diagram questions whenever doing so will help you solve it faster and with more certainty (which, for me, is most of the time). There are certainly questions that you can confidently answer correctly without diagramming their conditional reasoning and in which diagramming is unlikely to speed you up. If that's the case, it's not necessary to diagram.

It sounds like, at least some of the time, you're better able to answer some questions without diagramming. I think that's ok - but know that you shouldn't give up on diagramming until you've learned how to do it correctly and gotten comfortable doing so. For example, you had a hard time here dealing with the 'some' and 'most' statements - they don't have to throw you for a loop, we can deal with them in diagramming. If you decide never to diagram questions that contain 'most' and 'some' statements, you'll be doing yourself a disservice. Instead, I would recommend learning to recognize and diagram them easily - then, and only then, if you decide it's not worth your time, you can probably trust your instinct.

For the answer to your final question, see the discussion at the link above.

Hope this helps!

[rowdy]

I read through the thread and it was helpful to see it laid out correctly. Thank you!