#8 - Most people invest in the stock market without doing

[otanriverdi]

Hello:

Can you please explain Dec2000 -S3- Q8? Since it is a must be true question, the answer MUST be true. However, for me, answer A is could be true and not must be true. Can you please explain?

Thank you,

OT

[Dave Killoran]

Hi OT,

Thanks for the question. The justification for (A)--which indeed must be true--is based on combining the first and last sentences. Those two sentences appear as:


Invest in stock market do no research of their own

and

Invest in stock market make a profit


Because the two share a common term, we can combine them (which, due to the graphical restrictions of the forum won't be pretty, but it will work):


do no research of their own
Invest in stock market
make a profit


This "double-most" scenario where the "mosts" lead away from a common term always yield the inference that the two terms at the end are in a "some" relationship. For example, consider the following:


B
A
C


This yields the inference that some Bs are Cs. Why? Because of numbers. Let's say there are just 3 As. If most are Bs, then at least 2 are Bs. If most are Cs, then at least 2 are Cs. Thus, there is going to be an overlap, and at least one B will be a C.

Taking that logic, when we go back to the December 2000 question, we get:


do no research of their own make a profit


"Some" of course reverses, and that leads to:


make a profit do no research of their own


That's exactly what (A) says, and so we have proven that it must be correct.


Also, for the purposes of clarity, I separated your other two questions out, and answered them over here: http://forum.powerscore.com/lsat/viewto ... =12&t=3592

Please let me know if the above helps. Thanks!

[otanriverdi]

Thank you! I see now!

[SherryZ]

Hola amigo, thank you for your help!!

Dec 2000 LSAT, Sec 3 LR, Q8:

I eliminated answer choices B, D, E, but hesitated between A and C. Unfortunately, I chose C which is incorrect.

Could you tell me how to analyze this question quickly and effectively? AND why C is wrong??

Thank you very much!!

Abrazo,
Sherry

[BethRibet]

Hola Sherry,

Thanks for writing in!

What we know from the stimulus is that most people invest in the stock market without doing independent research, and that the majority of investors make a profit. If both of these statements are true, it must also be true that at least some in the category who make a profit (the majority) overlap with some in the category who invest without research (most). This is the case because there would not be a way for most (which indicates well over 50%) to be in one category, which did not include any of the majority (51% or more).

Answer choice A just states that there are "some" people in both categories, which as noted, must be correct.

Answer choice C discusses a subset of investors -- the "some" in the stimulus who research, but rely on other things in investing. With this subset, we don't actually know that this group has to overlap with "the majority" who make a profit. Some can reference a small group potentially, and "the majority" does not equate to all, so it could be this small group is not among the majority who do make a profit. Therefore, we can not assume that C is true.

Hope this helps!

Beth

[curiosity]

I understand now why A is the answer - because the two "most" statements have to overlap right?

But why is B wrong? The second statement says that "some of THESE people" meaning the aforementioned majority who invest in the stock market without doing any research of their own. Since the second sentence splits this majority into two categories, why is B wrong?

[Lucas Moreau]

Hello, curiosity,

Good question! You are correct in that "these people" refers to the "most people" who invest in the stock market without doing any research of their own. But B splits that group into four categories:

"Some" people who rely solely on their broker's advice
"Some" people who make decisions merely on hunches
"Others" (read: some people) who do some research of their own but also often rely on hunches or brokers
"A few" (also some) who always do research

We have no idea what percentages all these people are. We can't say for sure that B must be true, because we don't know that, for instance, the third category of people, who switch up their methods and do not rely solely on hunches or brokers, doesn't make up 90% of the entire group.

Hope that helps,
Lucas Moreau

[kgalaraga93]

Hi there,

I got this question wrong but when I initially answered it I did not use conditional reasoning and I realized that I needed to use it but am still unsure as to how to set it up. Here's what I have so far:

ISM = Invest in Stock Market
BA = Broker's Advice
RH = Rely on Hunches

MOST
ISM ---> No Research ----> BA
(branching into 2) ------> RH

FEW
ISM ----> Research -----> BA
(branching into 2) ------> RH

Drawing all this out I still had trouble making any kind of inferences. Help with this would be greatly appreciated. Thank you!

[David Boyle]

Hi there,

I got this question wrong but when I initially answered it I did not use conditional reasoning and I realized that I needed to use it but am still unsure as to how to set it up. Here's what I have so far:

ISM = Invest in Stock Market
BA = Broker's Advice
RH = Rely on Hunches

MOST
ISM ---> No Research ----> BA
(branching into 2) ------> RH

FEW
ISM ----> Research -----> BA
(branching into 2) ------> RH

Drawing all this out I still had trouble making any kind of inferences. Help with this would be greatly appreciated. Thank you!

Hello kgalaraga93,

Your diagramming has some accuracy although I don't think it diagrams everything in the stimulus, and I can't clearly interpret all your diagramming.
However, one may be able to do this problem commonsensically, without too much diagramming. The passage has a lot of vague stuff, saying "some" people do this, and "a few" people do that, etc. Two of the firmer guideposts are in the first and and last sentences, about "most" or a "majority". With these overlapping things, "most" not doing research but a "majority" making a profit, that guides you to answer A, "Some people who make a profit on their investments in the stock market do so without doing any research of their own", since you know there must be an overlap between the majority not doing research, and the majority making a profit.

Hope this helps,
David

[Johnclem]

Hello powerscore,
A quick question with diagraming this one.

Normally the word "without " indicates a necessary condition in which the sufficient condition gets negated .
Here we're not doing that . Is it because it's a "most " statement and that some and most don't get negation or contrapositives,?

Ppl invest -<MOST -> ~ research

Vs
Ppl do not invest <MOST> research


Thanks
John