#15 - Zack's Coffeehouse schedules free poetry readings

[ronnieronnie]

Hey Guys,

So I am reviewing my last practice test, wrong and right answers, as per Nikki advice, and already I am finding I need the explanations for multiple problems. Can I find these online somewhere? Or should I just list them here and you guys can help me out? If I can find them online it would be great if you guys could tell me where. But just in case they aren't on here, here are the problems I re-picked wrong answers for or didn't quite understand:


#15 ( I consistently pick E after going to pick D, but second guessing myself. I am uncertain whether "almost all" and "all day on most if not all" are equivalent or whether I am picking too strongly worded an answer choice. I keep thinking some is the right choice, because Zack' doesn't always have a Poetry Reading on Wednesdays, and in the logical opposition lesson some is not-all. Is this an incorrect understanding. Should I be thinking of some instead as not none?)


Thanks in advance guys!
Ronnie

[Nikki Siclunov]

Ronnie,

Finding answer choice (E) attractive on Q. #15 requires making three separate logical errors:

(1) "Almost every Wednesday" is equivalent in meaning to "all day on most if not all Wednesdays." There is no way to tell if on some Wednesdays Zack's doesn't have poetry reading: "almost every" could mean "every," just like "most" could mean "all." In other words, it is possible that there be free poetry readings on every single Wednesday.

(2) Even if we assume that there are some Wednesdays on which Zack's scheduled no free poetry readings, there could still be paid poetry readings. We just don't know. According to the last sentence in the stimulus, as long as Zack's scheduled a poetry reading (of any kind), they will be offering half-priced coffee all day:

Poetry Reading --> Half-priced Coffee

(3) Even if on some Wednesdays there were no poetry readings at all, (E) would still be incorrect. Do you see why? Just because the sufficient condition does not occur, that does not mean that the necessary condition wouldn't occur. Answer choice (E) commits a Mistaken Negation.

Hope this helps!

[al_godnessmary]

Looking through these answers really helped, although it made me come up with a question about the most train:

Wednesday Poetry 1/2 Coffee
Therefore: Wednesday 1/2 Coffee

Is it possible to take a contrapositive on this one (something that involves )???

[Nikki Siclunov]

Hi al_godnessmary,

No, contrapositives do not apply to or statements. Contrapositives are inherent inferences that apply to strictly conditional, absolute statements in the form of A B. Just because the coffeehouse has 1/2 coffee on most Wednesdays doesn't mean that lack of discounted coffee establishes that it is not Wednesday. It could be! "Most" doesn't mean "all."

Hope this helps!

[EL16]

Hi,

I have read through the discussion above and think I understand why D is correct over E. Just to confirm I understand one of the main issues I had here, is it correct that if you negate 1 side of a "some" statement, then you must also negate the other side?

For example, in #15 here, in the premise it is Wednesdays 1/2 priced coffee
So we could then infer Wednesdays 1/2 priced coffee
But we CANNOT then do what E is saying where we negate only the coffee, making this diagram say Wednesdays NOT 1/2 priced coffee

In other words, E is only negating the 1/2 priced coffee side, and therefore it is incorrect? If it negated both "Wednesdays" AND "1/2 priced coffee" (NOT Wednesdays NOT 1/2 priced coffees), would it be correct then?

Thank You,
Elana

[AthenaDalton]

Hi Elana,

We know that if a poetry reading is scheduled, then there's half-priced coffee:

Poetry reading Half priced coffee

The negation of that statement is, if half-priced coffee is NOT being offered, there's not a poetry reading that day:

NOT half-priced coffee NOT Poetry reading

We actually don't have enough information from the stimulus to say for certain that on some Wednesdays, half-priced coffee isn't on the menu. We do know that "almost every" Wednesday is a poetry reading day, which also means it's a half-priced coffee day.

But we don't have any information about what other days half-priced coffee may be offered on -- the half-priced coffee special is definitely available on poetry reading days, but it may also be available at other times too.

For this reason, we cannot say that if it's not Wednesday, it's not a half-priced coffee day.

I hope this makes sense. Good luck studying!

[jessicamorehead]

Can someone please explain this most arrow thing to me? I've posted before last week on a different question about it, but no one responded. Why is "most" a one-way arrow, but "some" goes both ways? How do you read it? For ex: does the most apply to the sufficient side or the necessary? Please help me understand the difference and how to diagram/read those two!

[Jon Denning]

Sure thing Jessica!

Most is a one-way arrow because the majority only applies to one of the pieces (the one at the beginning of the arrow). For instance, if I say that "most Californians are blondes," that tells you something about the people in California—the majority of them have blonde hair—but not about blondes: we don't know that the majority of blondes live in California.

Some, on the other hand, just means (in this context) "at least one in common," so it applies to both groups! If one group is a part of the other, then they're necessarily a part of each other...there's a point of overlap, in other words.

So from an arrow perspective, the "most" has a single arrow and describes the sufficient/starting side of the arrow. The majority of that piece is included in the other. "Some" is a double arrow since it applies to both pieces in the relationship, as they each are a part of one another.

Finally, with both "some" and "most" all we know is the minimums. "Some" means "at least one," but can be more: it's essentially anywhere from 1-100%, with the 1 guaranteed. "Most" means "more than half," so it's at least 51%, but also can be more (again, up to 100%). In short, don't assume "some are" implies "some are not" or that "most are" implies "a minority are not." Those are traps of the test makers will try to get you to fall for!

[LSAT2018]

Sure thing Jessica!

Most is a one-way arrow because the majority only applies to one of the pieces (the one at the beginning of the arrow). For instance, if I say that "most Californians are blondes," that tells you something about the people in California—the majority of them have blonde hair—but not about blondes: we don't know that the majority of blondes live in California.

Some, on the other hand, just means (in this context) "at least one in common," so it applies to both groups! If one group is a part of the other, then they're necessarily a part of each other...there's a point of overlap, in other words.

So from an arrow perspective, the "most" has a single arrow and describes the sufficient/starting side of the arrow. The majority of that piece is included in the other. "Some" is a double arrow since it applies to both pieces in the relationship, as they each are a part of one another.

Finally, with both "some" and "most" all we know is the minimums. "Some" means "at least one," but can be more: it's essentially anywhere from 1-100%, with the 1 guaranteed. "Most" means "more than half," so it's at least 51%, but also can be more (again, up to 100%). In short, don't assume "some are" implies "some are not" or that "most are" implies "a minority are not." Those are traps of the test makers will try to get you to fall for!

So if this question wasn't a chain like the one below:
Most Wednesdays → Free Poetry Reading → Half Price Coffee
but instead something along the lines of:
Some Wednesdays → Half Price Coffee

Answer (E) is still incorrect because you cannot infer about what is NOT. So given this example, answers like these can immediately be eliminated for Must Be True questions?

[Dave Killoran]

So if this question wasn't a chain like the one below:
Most Wednesdays → Free Poetry Reading → Half Price Coffee
but instead something along the lines of:
Some Wednesdays → Half Price Coffee

Answer (E) is still incorrect because you cannot infer about what is NOT. So given this example, answers like these can immediately be eliminated for Must Be True questions?

That is correct! Some can be All, and so Some Wednesdays could mean All Wednesdays.

Note also that we'd diagram that as: Wednesdays Half Price Coffee

Thanks!