#23 - Teachers are effective only when they help their

[Administrator]

Complete Question Explanation

Cannot Be True—SN. The correct answer choice is (E)

This stimulus contains several conditional statements, the first two serving as premises for the conclusion. The first states that teachers are effective only when they help their students become independent learners. Expressed as a conditional statement, the sentence can be rewritten as “if a teacher is effective, then they help their students become independent learners.” Additionally, this statement can be diagrammed as follows:

• TE HSBI

The second conditional statement appears as “not until teachers have the power to make decisions in their own classrooms can they enable their students to make their own decisions.” Simplified into a direct conditional statement, this may be rewritten as “if teachers enable their students to make their own decisions then they have the power to make decisions in their own classroom.” The diagram for this statement might be expressed as follows:

• TESMD PMD

The final conditional statement, also the conclusion of the stimulus is written as, “if teachers are to be effective, they must have the power to make decisions in their own classrooms.” This statement can be diagrammed as:

• TBE HPMD

The question stem then asks us to determine what can not be true of teachers who have enabled their students to make their own decisions. It is no accident that the question stem requires the reader to have an understanding of the most complexly worded conditional statement. Diagramming of that conditional statement has revealed that teachers who have enabled their students to make their own decisions have the power to make decisions in their own classrooms; look for an answer choice that reflects this.

Answer Choice (A): We know that students’ capability to make their own decisions is essential to their becoming independent learners. We do not know that their being given that capability necessarily indicates that they will become independent learners. As a result, we can not be sure if the students of teachers who have enabled their students to make decisions will or will not become independent learners.

Answer Choice (B): Given the information in the stimulus, we can not determine whether teachers who have enabled their students to make their own decisions are effective or ineffective teachers. The only thing we can say with certainty regarding effective teachers is that if a teacher is effective, then they help their students become independent learners. Conversely, the contrapositive of that statement would allow us to say, “if a teacher can not help their students become independent learners, that teacher is not an effective teacher”

• (HSBI TE).

Neither statement tells us anything about teachers who have enabled their students to make their own decisions being effective or not effective.

Answer Choice (C): This answer choice is incorrect for the very same reasons as answer choice (B) below.

Answer Choice (B) is incorrect. The teachers in question could be effective or they could be ineffective; we simply can not tell given the information in the stimulus.

Answer Choice (D): Not only does this answer choice fall under the category of “could be true,” but it in fact must be true given our diagramming of the conditional statements.

Answer Choice (E): This is the correct answer choice. We know that teachers who have enabled their students to make their own decisions have the power to make decisions in their own classroom. Therefore, this answer choice can not be true and is the credited response since the question stem has asked us to find the one answer choice that does not fall under the definition of “could be true.”

[gargantua]

Hi,

Powerscore LSAT Test Prep books have helped me understand the LSAT in ways I thought I would never understand. Thank you.

Could you explain how to diagram the second premise? Does the "until" really introduce a negated sufficient condition and the necessary condition is after "can" which is negated as well?

When I try the diagram this way, make a contrapositive, put the premises in a long conditional chain, it makes logical sense with what cannot be true, but I do not understand why "until" is not introducing a necessary condition with a sufficient condition being negated.

[Steve Stein]

Hi Gargantua,

First, thank you for your kind words about our books--I'm glad that you've found them so helpful.

As for until, let's consider a simpler example:

"I cannot drive my car until I fix my flat tire."
(or, "until I fix my flat I cannot drive my car")

What does this really mean?

That if I haven't yet fixed my flat, I cannot drive my car:
fix flat drive car)
And if I am driving my car, I must have fixed my flat:
drive car fix flat


Tricky stuff, so please let me know whether this is clear--thanks!

~Steve

[jm51]

Hello,

I was hoping I could get some help on how to diagram the second sentence. The LR Bible states that when "until" is used in a sentence, "whatever term that is modified by until becomes the necessary condition, and the remaining term is negated and becomes the sufficient condition."

Using that method, I arrived at this for the 2nd sentence:

~SD --> TPD

But that's not what will help me make the chain of inferences that I need to arrive at. Am I missing something? Does the inclusion of "NOT" before the until change things? I'm thinking that the "not" before until is applied to the students making their own decisions, and thus when that is negated you arrive at:

SD --> TPD

Thank you so much for your help!!

[BethRibet]

Hi Jm,

Thanks for the question.

Your latter reasoning is correct -- this should be SD --> TPD.

If you focus on the meaning of the sentence, it's telling us that if students are enabled to make their own decisions, it must be true that teachers have the power to make decisions.

Sometimes the convoluted phrasing can get test-takers turned around or confused; when this happens, try to focus on what we know to be true of the two conditions, based on what's written.

More mechanically, while it's helpful to remember the rule that with except, unless, until, or without we negate the condition which is not the necessary one (the one not modified by one of those 4 words) in order to get the sufficient condition. But the word "not" here generates an extra negation, so "Not until A will B happen" is in meaning, the same as "Until A happens, B will NOT happen". Either way it becomes: B --> A

Hope that helps!
Beth

[oops27]

Hello powerscore,

I'm a little confused how the argument as diagrammed is valid. Above it's diagrammed as:

Premise 1: TE---->HSBI or "if a teacher is effective, then they help their students become independent learners.”

Premise 2: TESMD---->PMD or “if teachers enable their students to make their own decisions then they have the power to make decisions in their own classroom.”

Conclusion TBE----->HPMD or “if teachers are to be effective, they must have the power to make decisions in their own classrooms.”

I thought that this sentence was a part of the chain too: "Student's capability to make their own decisions is essential to their becoming independent learners." I think that this helps connect premise 1 to premise 2; I diagrammed it as "Independent Learners--->Make their own decisions."

Does this diagram work?

1) Teachers effective----->HSIL (Help their students become independent learners)
2) ESMD (Teachers enable their students to make decisions)------>THP (teachers have the power)
3) IL (if independent learners)----->MD (capable to make decisions)
Conclusion: Teachers Effective--->Teachers Have Power

Then, I connected 1-3-2-conclusion
Teachers effective---->Help students become independent learners
Independent Learners---->capable to make decisions
Teachers enable students to make decisions--->Teachers have the power
Conclusion: Teachers effective---->Teachers have the power.

Does this work or am I just making connections out of thin air? Thanks so much as always for your help, and especially the "not unless" discussion above, which was very helpful.

[James Finch]

Hi Oops,

Yes, you could chain the following together to get what the conclusion gives us:

TE SIL SMD TMD

or as the conclusion states:

TE TMD

However, this Must Be True question asks for a contrapositive of one of the conditional relationships on the interior of the chain, so the completed chain only becomes useful if you write its entire contrapositive:

TMD SMD SIL TE