LR Bible error? p. 330 top of the page Forum

[greenchair]

LR bible says the following cannot yield an inference, EVER:

D <--SOME--> Y <--MOST--> S


Why not?

D <--SOME--> S

seems to be a logical inference.



D=DAIRY
Y=YOGURT
S=SWEET

Some dairy products are yogurts. Most yogurts are sweet.

Then it MUST be that some dairy products are sweet --- right?

[mickeyD]

I'm sure you mean LR bible instead of LG, but the LR bible method does work for this question.

I have taken out the second premise about noneccentric lecturers because it is unnecessary to find the correct answer.

1) Diagram

Lecturer who is effective teacher ---M---> Eccentric
Effective teacher ------> Good Communicator

2) Link the variables. You can safely assume that lecturers who are effective teachers fall under "Every effective teacher"

GoodComm <------ Lecturer&EffectiveTeacher ---M---> Eccentric

3) Convert to some train. This answer requires you to convert "Most" to "Some."

GoodComm <------ Lecturer&EffectiveTeacher <---S---> Eccentric

4) Connect the train. Start from Eccentric and go to Good Comm.

GoodComm <---S---> Eccentric

5) Answer. You can say that some good communicators are eccentric, and some eccentric people are good communicators. The correct answer is the former.

[greenchair]

Wow mickyD... thanks...

For some reason, in my head, I didn't think I could switch the direction of the arrows.....

[greenchair]

I didn't mean to change the forum topic on you, MickeyD... but you did answer my question. But I still have a question about my new forum topic...

[mickeyD]

Don't worry about it, and that is not an error. The best way is to just think of an example.

Some presidents are black. Most black people are in jail.

Conclusion: Some presidents are in jail.

You cannot assume this. Just because majority of black people are in jail, doesn't mean that the one who is the president necessarily has to be one of them. If there are 500 black people, and 251 of them are in jail, Obama could easily be one of the 249 that aren't in jail.

And this is obviously a joke, please don't kill me haha. I'm a minority, I used the example to make the point clearer.

[mickeyD]

Also, perhaps a less offensive example may help.

Some Republicans are celebrities. Most celebrities are Democrats.

(incorrect) Conclusion: Some Republicans are Democrats.

[greenchair]

Yeah, that was pretty offensive, but I get it. Thanks for the help!

[Nulli Secundus]

Your example is unnecessarily confusing you, if you think about it as all dairy products in the universe, you might think at least some of those are sweet yogurts indeed. But LSAT deals with small samples, like dairy products on a shelf. While some of dairy products on a shelf may indeed be yogurts, they may or may not be sweet, therefore you cannot assume.