# Conditional Question

#### jetztodernie

##### Conditional Question
« on: October 09, 2010, 10:12:03 AM »
Conditional linkage and inferences have always been my weakness.  I have something that i'd like verified.  Thanks!

J --> S
S --> J
does NOT equal J <--|--> S

J --> S
S --> J
DOES equal J <--|--> S

Simply because of 'necessary' vs 'sufficient' differences.

Is this correct?

#### Jeffort

• 89
• LSAT Tutor
##### Re: Conditional Question
« Reply #1 on: October 09, 2010, 12:41:32 PM »
Conditional linkage and inferences have always been my weakness.  I have something that i'd like verified.  Thanks!

J --> S
S --> J
does NOT equal J <--|--> S

J --> S
S --> J
DOES equal J <--|--> S

Simply because of 'necessary' vs 'sufficient' differences.

Is this correct?

Your conclusions are correct.  The first situation basically means that you have to have at least one of the two (J and/or S) and does allow you to have both, whereas the second situation establishes that J & S are mutually exclusive to each other, meaning that you cannot have both of them selected, but it does allow for having neither of them in the in group.

Did you just work the infamous birds in the forest in/out grouping game?  cuz that is where to get the frequently talked about ~J ---> S rule from.

#### jetztodernie

##### Re: Conditional Question
« Reply #2 on: October 09, 2010, 06:03:18 PM »
Precisely!  Im going through the LG Bible and came across it.  Thus far, this type has been the most difficult for me.  Modified it a bit for my purposes...

Scoring very well on the LR and RC (~2-3 wrong), so focusing a lot of effort on games.  And, because it's my weak spot, focusing a lot of that on conditionals.

#### jetztodernie

##### Re: Conditional Question
« Reply #3 on: October 11, 2010, 11:10:53 AM »
Another!

M <--|--> O  (If M, no O; If O, no M)
M <--|--> N  (If M, no N; If N, no M)

This does NOT mean      O <--|--> N      because you could have an N and still perhaps have an O.

The reason im asking these questions because im trying to write down a cheat sheet for when i study.  So that i can look at it, reference the rules, and then apply the rules until they become second nature and the cheat sheet is irrelevant and unnecessary.  Therefore, I'm trying to figure out if the above examples are ALWAYS the case.

#### jetztodernie

##### Re: Conditional Question
« Reply #4 on: October 13, 2010, 07:50:27 PM »
Also...

If Z morning, then L morning (Zm --> Lm)
Contra: if not L morning, then not Z morning  (~Lm --> ~Zm)

But does that necessarily mean that:
If L afternoon, then Z afternoon

When morning and afternoon are the only 2 slots available?

#### jetztodernie

##### Re: Conditional Question
« Reply #5 on: November 13, 2010, 01:56:11 PM »
Another question:

AandB -->  Z
~Z -->  ~AorB

X --> ~Xor~Y
XorY --> ~X

Are those correct?

Is there a quick answer to this?  "And changes to 'or' but 'or' stays the same."  That's what it seems like to me.

#### marcus-aurelius

• 349
##### Re: Conditional Question
« Reply #6 on: November 13, 2010, 02:20:52 PM »
I do believe or changes to and.

If A then B or C (means with A you have either B or C or both but at least one)
thus
If ~B and ~ C then ~A  (for if you do not have B and C, you cannot have A since one is required.

If or stayed the same, the contrapositive would be

If ~B or ~ C then ~ A (but it is possible to have ~B and still have A if C is present)

As for your example, you have

If X then ~X or ~Y  (This really says if X then ~Y for you can never have X and not have X at the same time).

#### Julie Fern

• 25797
• hillary clinton say "boo!"
##### Re: Conditional Question
« Reply #7 on: November 16, 2010, 06:25:22 AM »
if julie nice pinheads, then julie encourage them.

therefore, julie win.

#### MEMEMEME

##### Re: Conditional Question
« Reply #8 on: November 17, 2010, 04:50:20 PM »
Red herring, Julie.

#### Julie Fern

• 25797
• hillary clinton say "boo!"
##### Re: Conditional Question
« Reply #9 on: November 18, 2010, 05:39:53 AM »
salmon, memememe.