@Call Me Eric I would always include the modifier when assessing my subject. In this example I would always think of it as 'some students' not just 'students.' This will remind you that the modifier 'some' is what is important to this question -- not the word students. The question can say 'some students can read,' 'some apples are sweet,' 'some dogs are small," and in every case [some = at least one] and so each different version could be satisfied by one student reading, one apple being sweet, or one dog being small. It is the modifier that is relevant.

Also, like I mentioned above -- Logic and English are two different languages. In English, the word students is plural and thus demands that more than one student be able to read. In Logic the modifier Some overrides the plurality of the word students. In the language of logic the quantifier 'Some' always means at least one, nothing more, nothing less.

There are certain elements of the language of logic that do not have a 'comfortable' explanation when compared to the rules of the language of English. The rule that 'some equals at least one' is one of them. Memorize the rule and accept that (when using the language of Logic) it just is what it is and this type of problem becomes much easier. Hope this helps :)

#feedback

It would be great to have the same hi-lite and underline tools available in 7Sage's built in Notes feature that we have when doing the LSAT practice questions and that we will have when taking the actual test.

I'd like to be able to hi-lite and underline in my notes when working through a problem alongside the video, using the same tools that will be on the real-life exam.

Right now the Bold, Italics, Strikethrough, and Quote options do come in handy -- but having Underline and Hi-Lite added would be a huge bonus!!

@duncan.aronson

The implication in Choice B is that what is causing the kids in the EEP program to do better in school, is not the EEP program itself, but being raised by a parent who has a background in education. 

This weakens the argument that EEP programs are successful and should be expanded. 

This is due to the fact that, in the case a child was in an EEP program being taught by a parent who did not have a background in education, there would be no additional benefit to the child and they would not have a higher school performance than average. 

Choice B offers an alternative hypothesis (having parents w/ an education background is actually what is helping children achieve above average school performance), which weakens the argument. 

--------------------------------------------------

Answer Choice E addresses children that were not in the EEP at all. It says that some of them do incredibly well in school. However, since they did not do the EEP they are ‘outside’ the correlation. They are, literally, outliers. The existence of outliers does not weaken correlation.

--------------------------------------------------

@Richard Santa-Cruz I also got #3 wrong the first time around.

A few things that helped me to understand why:

1. Conditional relationships are different than Causal relationships. In my mind I was operating under the assumption that

   a --> b = a -c-> b

   and this is not the case. So getting that clarity was helpful.

2. I re-phrased the question as

   A group of people ate day-old sushi.

   All of the people in this group also had food poisoning the next day.

   By phrasing the question as two separate ideas it helped me to see that while two events happened to the same group of people, we can't see from the language that one event definitively caused the other. For me, the word 'also' represents two ideas that might be connected but are still separate.

Hope that's helpful!

@DiegoAntonio @StanHolt

The reason that question 5 does not use the Two Most argument form comes down to context.

Premise 1: Most potion's in the witch's hut are poisonous.

Premise 2: Most potions have some beneficial effects.

In Premise 1 we are discussing ONLY the potions in the witch's hut.

In Premise 2 we are discussing ALL the potions in existence.

Thus, just knowing that most potions inside the witch's hut are poisonous does not give us enough information to infer how that impacts all potions in existence.

It could be that all the potions in the witches hut make up only 1% of potions in existence. So even if all the potions in the witch's hut are poisonous, it does not mean that it is a most statement in relation to all potions in existence.

When looking at Premise 2, we see that most potions (of all the potions in existence) have some kind of beneficial effect. However, we don't know that any of these potions with a beneficial effect are within the Witch's hut. It actually seems unlikely, since we know most of her potions are poisonous.

However, there is no way to know either way.

That is why there is no valid conclusion. We don't know what percentage of potions in existence are inside the witch's hut.

This means that, at best, we can draw "some" conclusions using Premise 1. We know that some potions (in existence) are poisonous, because the poisonous potions in the witch's hut exist and thus we know that at least 1 poisonous potion exists. Since 'some is at least 1,' we know that some poisonous potions exist.

However, we have no idea what percentage of the existing potion population is made up of the potions within the witch's hut. We would have to know with absolute certainty that the percentage of potions within the witch's hut made up 51% (or more) of the existing potion population for this to be a Two Mosts argument form.

I'm confused about the diagramming of question #4. I watched the video and the diagram looks incorrect regardless of whether you choose to use the Some Before All or Most Before All structure for the diagram.

In a Most Before All argument the diagram should be as follows:

Premises:      

A -m—> B

B —> C

Conclusion: 

A -m—> C

In a Some Before All argument the diagram should be as follows:

Premises:      

A <—s—> B

B —> C

Conclusion: 

A <—s—> C

The diagram for question #4 ends up looking like this (using the Most Before All format):

Premises:

Potion in Hut -m--> Poisonous

(A) -m--> (B)

Potion in Hut --> Some Benefit

(A) --> (C)

Conclusion:

Poisonous <--s--> Beneficial

(B) <--s--> (C)

We end up with a conclusion that says

Some (Bs) are (Cs) instead of a conclusion that says some (As) are (Cs) -- which is the valid conclusion.

Can anyone #HELP me out here to understand why this is valid?

@goonkstr The two people who have already replied both gave great answers in saying that the question stimulus does not give us enough information to reasonably infer that any company is using 'all' their resources towards making a new vaccine.

I also wanted to point out that your logic is 'backwards' in your question.

"I felt like it was a reasonable assumption that investing all resources into developing a vaccine means you're racing to develop it."

Based on what you've said you're making the claim that 'investing all resources into development' is a Sufficient Condition for the Necessary Condition of 'racing to develop a vaccine.' This is fair.

However, while Sufficient Conditions guarantee Necessary Conditions, Necessary Conditions do not guarantee Sufficient Conditions. All the Necessary Condition does is allow for the range of potential Sufficient Conditions that could satisfy the Necessary Condition.

The question stimulus gives us the Necessary Condition [businesses are racing to develop the vaccine], but it does not give us enough information to know which Sufficient Condition is the 'right' one.

This is why we then have to infer what the Sufficient Condition would be based on context. We have to choose the best answer, even if there are other answers that could work.

In this case, I think that answer choice B is the best answer because to say 'working on a vaccine' encompasses a myriad of possible Sufficient Conditions. Answer choice C is very limited because it dictates that a company must be 'investing all their resources,' which is a specific Sufficient Condition.

A company that is 'investing all their resources' on the vaccine is under the umbrella of those companies that are 'working on' developing a vaccine. However, a company that is 'working on' the vaccine is not explicitly included in the group of companies that are 'investing all their resources.'

Answer choice B allows us to choose the superset, while answer choice C only allows us to pick a specific subset. Therefore, answer choice B is the best answer.

Hope this helps :)

@aakash2003ch457

The indicator words 'Some' and 'Most' are indicative of ranges.

The range of 'Some' goes from the lower boundary of 'at least 1' to the higher boundary of 'including all.'

The range of 'Most' goes from the lower boundary of '50%+1' to the higher boundary of 'including all.'

Because these indicators represent range, it is impossible to know for certain what specific value is being represented. We just know that the value falls within a certain range.

The indicator word 'All' does not indicate a range, and instead indicates an explicit and specific value. Seeing the indicator word 'All' tells us, with certainty, a numerical value.

Ex. There are 100 women at the hair salon. Some women have come for haircuts.

[There's no way to know how many women are their for haircuts, all I know is that the number of women who came for haircuts is within the range of 2-100.]

Ex. There are 100 women at the hair salon. Most women have come for haircuts.

[I am still not able to know the definitive number of women who are in the salon for hair cuts. All I know is that the number of women who came for haircuts are in the range of 51-100.]

Ex. There are 100 women at the hair salon. All of the women have come for haircuts.

[Only in this example am I able to know, with certainty, the number of women who have come for haircuts. I know there are 100 women. I know that 'all' is a definitive indicator that gives me a specific numerical value. I know that all 100 women came for haircuts]

The reason that 'All' is considered a stronger claim than 'most' or 'some' is because 'All' guarantees a specific value (in this case 100), while 'most' and 'some' only show that any numerical value within a certain range (2-100 or 51-100 depending on the example) can be considered logically valid.

Hope this helps :)

@Dbarsemian You are operating under an incorrect assumption in your example.

"Many people (for example) means that its above a certain majority"

This is not true in Logic or in English. There is no rule in either language that states that 'many' is an indicator of proportion, or of a proportional majority.

In Logic specifically, all the word 'many' means is 'a large amount.' There can be a large amount of something without that amount representing a proportional majority.

'Most' indicates a proportional majority and that is why the lower boundary for 'Most' statements is 51% or more.

---------------------------------------

Ex. 70,000 fans came to see the Los Angeles Rams play at SoFi Stadium. Many of the fans are from Los Angeles County.

-- this example uses the quantifier of 'many'

-- when we see 'many' all we know is that it means a 'large amount'

-- Therefore, we can't know if the number of fans that are from Los Angeles county is 1000 (a large amount of people) or all 70,000 (also a large amount of people)

-- When we see 'many,' we understand that there is a range -- but there is not a sharp lower boundary to that range -- it is entirely up to the interpretation of the reader.

Ex. 70,000 fans came to see the Los Angeles Rams play at SoFi Stadium. Most of the fans are from Los Angeles County.

-- if I change the quantifier to 'most' the way that we would interpret the sentence changes entirely and now must operate within a specific framework

-- we know that 'most' has a sharp lower boundary of 50%+1

-- we also know that 70,000 fans are in SoFi stadium

-- so, this 'most' claim has a sharp lower boundary of 35,001

-- we know for certain that at minimum 35,001 of the fans in SoFi stadium are from Los Angeles county, because 35,001 makes up the proportional majority (50%+1) of 70,000

-- In the previous example [using 'many'] we had no idea what the lower boundary was, and the number of fans in SoFi stadium from LA County could have been any number from 1000 to 70000 as long as it fit under the [subjective] umbrella of a 'large amount.' In this example we have the sharp lower boundary to inform us of some parameters.

---------------------------------------

I hope this helps to show the difference between 'many' and 'most.'

The value being described by 'many' is subjective and unknown and simply indicates 'a large amount.'

As said in the video, reasonable people can reasonably disagree. While I might say that 1,000 people is many people, you might say that 1,000 is not enough and that, really, 15,000 people is many people.

Neither of us would be objectively right or wrong and, knowing whether an LSAT question is describing 1,000 people or 15,000 people won't help or harm us in choosing the correct answer.

A value being described by 'most' is objective, but unknown.

We know that [within the language of Logic] the indicator 'most' is describing a specific value that is between 50%+1 and 100%.

If we are looking at a question in which the indicator 'most' is used and I say that 37% is most and you say that 51% is most -- then I would be objectively wrong and you would be objectively right, because my value of 37 is below the lower boundary of a 'most' statement and therefore outside the objective range of logically valid values.

If I said that 81% is most and you said that 51% is most, we would both be in that objectively correct range of logical validity [50%+1 to 100%]

I hope this helps :)

@VividQuenchingGift Logic is its own language. In English, some refers to a portion. In logic, some means 'at least 1.' This is true outside of the LSAT and if you take a Logic [especially Symbolic Logic] class at any point that is not related to the LSAT you will see that this rule is important when you get into more complex concepts.

Understanding the concept of 'some' as a range is incredibly important when using the language of Logic, because when we see 'some' we have to be able to hold in our minds the idea that it is anywhere between 'at least 1' and 'all.' A lot of the times we will never know what specific number 'some' represents, we have to train our minds to be okay with the idea of the range of some, which is the concept that is introduced in this video.

Some is not all. Some is at least 1 and can include as many as all. We do not know if it does. All is all, because the quantifier all lets us know for a FACT that everything in a set is included.

Some is possibly all, possibly most, possibly least, and at least 1. Some is not all, because we do not know what amount of a set is included.

--------------------------------------------

I'll use the example to try and make it even clearer:

There are 20 kids in Mrs. Troop's class. Some of the kids in Mrs. Troop's class can read.

So, first we know that Some = At least 1

So, if one kid in Mrs. Troop's class can read, then this logic is valid.

If 5 kids in Mrs. Troop's class can read, the logic is valid.

If 18 kids in Mrs. Troop's class can read, the logic is valid.

If 20 kids in Mrs. Troop's class can read, the logic is valid.

But then we get the question, if all 20 kids can read, why don't we use the quantifier All?

Because we don't know which one is true. When we see the quantifier some we must acknowledge that it exists as a Range.

Anything in the range of 1-20 (for this specific example) could make this statement logically valid. We don't know if some means 6 or some means 20. We just know that some means at least 1.

Since we don't know which one is true, then we can say that any are true, so we can say that all are true.

ANY number between 1 and 20 makes this a logically valid argument.

We do not have certainty that 20 kids can read. 20 kids could read, and that would satisfy the terms for logical validity, but 3 kids could read and that would also satisfy the terms for logical validity in this example.

Since we don't have certainty, we're not going to use All, but since there is the possibility, we use Some.

This is why Some can be as many as all.

--------------------------------------------

Also, I learned the concept of 'some is at least 1' in a logic class a while ago and I will say that all of the mental gymnastics that people try to do to escape from the fact that in Logic "some is at least 1" is just going to be confusing and not amount to anything.

Just do your best to accept it, get comfortable with the idea, and you'll be fine :)

@Bobby John

You are being asked to assess the rules of logic. The fact that the Necessary Condition does not guarantee the Sufficient Condition is one of the most basic and most important rules of logic.

Just because Kumar is more than 5 minutes past the final bell, does not guarantee that he will be issued a late citation -- because of the logical rule that the Necessary Condition does not guarantee the Sufficient Condition.

For me, using hypotheticals of the other things that could happen to Kumar (no one notices, he gets a warning, he had a hall pass, whatever) help me to see why the Necessary Condition does not guarantee the Sufficient Condition, because it shows me some of the other possible Sufficient Conditions that could exist in a valid logical relationship with the Necessary Condition.

However, if that is unhelpful to you -- then don't do it. Just use the rules of logic. We know that the Necessary Condition is being 5+ minutes late after the final bell. We know that the Sufficient Condition is being cited as late.

Therefore, we know, using the rules of logic, that Kumar being 5+ minutes late CANNOT guarantee that he was cited as late. Why? Because the Necessary Condition CANNOT guarantee the Sufficient Condition. The Necessary Condition makes all Sufficient Conditions possible, but does not guarantee any specific one.

If I were you I would do a lot more study on Necessary vs Sufficient conditions until you understand that concept backwards and forwards. The dog and mammal example that I used in my first response can be helpful.

Not sure how else to explain this, but hopefully it is more clear now.

@hsuyt25

While 'anyone' is not a specific Group 1 indicator, 'Any' is, so your instinct was right to use that as a translation tool.

In regards to your specific question about if

antibodies --> infected and 1 week

would also work, just translating it back into English shows you that it doesn't. If you translate that Logic into English you get something like

If one produces antibodies to fight the virus then, after a week, they are infected by the virus.

This is not what the original question stem is saying.

In the correct answer

Infected & 1 week --> antibodies

The conjunction of 'after a week' is a part of the Sufficient Condition because it guarantees the Necessary Condition.

For a person to produce antibodies they must 1) be infected and 2) be infected for more than a week

If 'after a week' becomes part of the Necessary Condition (like what you are suggesting in your incorrect answer), the conclusion does not follow from the premises and the argument is not logically valid.

Additionally, I would advise you not to think about hypotheticals or try to interpret/intuit additional scenarios that are not explicitly state within the question stem.

While it makes intuitive sense that we could argue that if someone has the antibodies then they must have been infected and it has been a week, this does not make sense when we translate the sentence exactly as it is written into logic.

As someone that is a more naturally intuitive thinker I also find it challenging at times to only focus exactly on the question stem, exactly as it is written -- but from what we've learned so far the best way to master the Logical Reasoning portion of the LSAT is to deal with things as they are written literally and not think about other intuitive possibilities/scenarios.

Hope this helped :)

@kyle.crail13@gmail.com

I think the issue that you are having is that you are conflating being legally allowed to buy alcohol in the US with the action of literally being physically capable of buying alcohol in the US.

If a 22 year old American is traveling in Europe, they are legally allowed to buy alcohol in the US. Are they physically capable of doing it at that present moment? No, because they are not in the US. However, their physical presence in the US does not impact the legality of whether they are allowed to buy alcohol in the US in general.

This question is discussing legality, not literal capability.

Hope this helps :)

@ellagrace88 If I'm ever confused about which condition is Sufficient and which is Necessary I literally ask myself 'which thing guarantees the other?'

In this example, a mastery of logic guarantees an improved score on the PrepTest.

Why? Simply because if you master material you are being tested on, your score will improve.

However, an improved score on a PrepTest does not guarantee a mastery of logic. Just off the top of my head other things that could help improve a PrepTest score

-- mastery of reading comp

-- changing study habits

-- starting a more intense study schedule

-- taking a new LSAT prep course

-- working with a private tutor

-- changing the location of where you take a PrepTest to a more quiet place with no distractions

^ all of these could be potential Sufficient Conditions that lead to the Necessary Condition of improving your score on a PrepTest.

When I was really drilling the concepts of Sufficiency and Necessity into my head something that helped was to remember that

The Necessary Condition makes all Sufficient conditions possible, but does not guarantee one specific Sufficient Condition.

vs.

The Sufficient Condition guarantees one specific Necessary Condition.

---------------------------------------

Couldn't it be assumed that if you didn't master it its not necessarily true that you didn't improve?

Also, to answer this specific question from your post --

you are altering the question stimulus, resulting in you trying to answer a question that is not being asked, making things more complicated for yourself. 

Your question translates to:

/Mastery --> /Improve

That is not in the question stimulus. The stimulus is only assessing the scenario of students who did master logic.

Which means the original question translates to:

Mastery —> Improve

If you take the contrapositive of both you get:

Your Question: Improve --> Mastery

Original Question: /Improve --> /Mastery

So, your question creates a completely new translation that is not a part of the question.

Furthermore, this new translation creates an error because

Improve --> Mastery

confuses the Sufficient and Necessary conditions. It implies that to improve your score on a PrepTest you must have gained full mastery of logic. However, like I said above, there are many alternative actions that could result in an increased score on a PrepTest.

I am also a pretty intuitive thinker and I found myself getting caught up in similar ways and kept trying to think about the question stims from multiple points of view. Once I stopped doing that and focused exactly on what the question was asking, nothing more and nothing less, I think I am doing a lot better!

Hope this helped :)

@qjmarron

The ability to cast the Hervicus charm is the necessary condition for mixing plant material into garden soil -- but only for the second sentence.

The answer key reads

Sentence 1

mixed --> increase

/increase --> /mixed

Sentence 2

mixed --> cast

/cast --> /mixed

The reason that these two statements cannot be linked together is because they have the same sufficient condition [plant material being mixed into garden soil].

To link together multiple conditionals there has to be at least concept in the statements that acts as both a sufficient and a necessary condition.

In this example, that doesn't happen.

Hope this helps :)

@Jennandjuice

/A --> S implies that if Joffrey does not kill Arya then he 100% will kill Sansa. (Same thing for /S --> A)

This is not true because he does not have to kill either Arya or Sansa.

All the statement is saying that he cannot kill both Arya and Sansa. That leaves Joffrey the option of killing Arya or killing Sansa or killing neither of them.

You are confusing the sufficient and necessary conditions.

A --> /S

^ In this case, Joffrey kills Arya [which is sufficient because he can only kill one of the girls] this then makes the fact that Joffrey will not kill Sansa [/S] the necessary condition, because he cannot kill both girls.

/A --> S

^ In this case, you are trying to argue that if Joffrey does not kill Arya [/A] then he must kill Sansa [--> S] but that does not logically follow. While it is true that not killing Arya [/A] is sufficient for meeting the needs of the statement "Joffrey cannot kill both Arya and Sansa," continuing with the [--> S] means that it is necessary for Joffrey to kill Sansa. This is not true. Joffrey could kill Sansa, but he could also do a bunch of of other things (the most obvious being to kill neither of the girls) and still exist within the logical confines of the statement.

Hope this helps :)

Okay, the Kumar example broke my brain at first, but I worked it out on paper and I want to share my thought process in case it helps anyone else.

-------------------------------------

First, let's break down the problem.

Sufficient Condition = being cited as late

important to note that we are talking about being cited as late, not just being late

Necessary Condition = arriving more than 5 minutes past the last ring of the homeroom bell.

[Late --> 5+]

-------------------------------------

I then had to go back to understand If vs Only If theory in super basic terms.

IF indicates the Sufficient Condition. This means that the First Event's occurrence guarantees the Second Event's occurrence.

Ex. If one is a cat [Sufficient Condition] then one is a mammal [Necessary Condition].

Being a cat guarantees being a mammal. It is not possible for one to be a cat without also being a mammal.

ONLY IF indicates the Necessary Condition, meaning that the Second Event's occurrence is required for the First Event's occurrence to be possible.

The occurrence of the Second Event [the Necessary Condition] does NOT GUARANTEE the occurrence of the First Event [the Sufficient Condition].

Ex. If one is a mammal, one is a cat.

[^^^^ This does not make sense. The Necessary Condition (being a mammal) does not guarantee the Sufficient Condition (being a cat). One could be a mammal, and not be a cat.]

What really helped me to understand this aspect of the Necessary Condition is that the Necessary Condition is what makes all Sufficient Conditions possible, but it does not guarantee any particular Specific Condition.

For example, being a mammal means one could be a cat, dog, horse, etc. Being a mammal does not guarantee that one is specifically a cat or specifically a dog or specifically a horse.

-------------------------------------

Okay, so back to the Kumar example.

First, I translated the symbolic logic of [Late --> 5+] back into English using the (if A --> then B) format.

"If a student is cited as 'late,' [Sufficient Condition] then they arrived more than five minutes past the last ring of the homeroom bell [Necessary Condition]."

This makes sense, the occurrence of the First Even [Sufficient Condition] guarantees the occurrence of the Second Event [Necessary Condition].

For a student to be cited as 'late' it is guaranteed that they arrived more than 5 minutes past the last ring of the homeroom bell. If a student did not arrive more than 5 minutes past the last ring of the homeroom bell, they would not be cited as late.

But, if we try to switch things around [like I did above with the cat and mammal example] things start to get wonky and do not work.

If a student arrived more than five minutes past the last ring of the homeroom bell [Necessary Condition], then the student is cited as "late." [Sufficient Condition]

This statement is not valid because the Necessary Condition does not guarantee the Sufficient Condition.

The same way that being a mammal does not guarantee being a cat, the behavior of showing up more than 5 minutes past the final ring of the homeroom bell does not guarantee being cited as late. It makes being cited as late a possibility, but it does not guarantee that that event will occur, because there are also many other possibilities that could happen.

I think part of the reason that I struggled so much to wrap my head around this is

1. I confused being "cited as late" with "being late" -- these are 2 very different things!

2. My confusion between "being late" and "being cited" stopped me from understanding the other possibilities of what could happen to Kumar.

The same way that being a mammal opens the possibility for being a cat, whilst also opening the possibility for being a dog, horse, etc.

Kumar being 17 minutes late opens the possibility for him to be 'cited as late' but it also opens the possibility for him to be given a warning, be given detention, for his teacher not to notice and nothing to happen, etc.

-------------------------------------

Anyways I know this was very long winded and repetitive, but it was only through thinking out the example in this in-depth way that I was able to understand where I originally went wrong :)