Law School Discussion

Please help me on this diagramming LR problem

Please help me on this diagramming LR problem
« on: December 09, 2010, 06:12:39 PM »
Hi All,

I am down between A and D and am having a hard time with connecting the variables when I diagram this problem.

June 2001, Section 1, #10

The conclusion follows logically if which of the following is assumed--question type.

This is how I diagrammed it.

SB--->SEN (contrapositive: no SEN-->no SB)
Student body must include some students with special educ. needs.

LD---> no SB (contrapositive: SB-->no LD)
No students with learning disabilities have enrolled in the school

Therefore the school is violating its charter.

I cannot make any diagramming connections and am stumped on this one. Can anyone please advise me on this? Thanks in advance....

My 2 choices
A) LD--->SEN
D) SEN--->LD

Re: Please help me on this diagramming LR problem
« Reply #1 on: December 10, 2010, 08:20:49 AM »
First, let’s analyze the stimulus:

The stimulus states that the school NEEDS students with special needs enrolled to fulfill its charter, but it does not have students with learning disabilities enrolled, so it currently violates its charter(no students with special needs enrolled)

1) The school needs students with special education needs enrolled.
2) The school has no students with learning disabilities enrolled
3) ?
C) Therefore, the school has no students with special needs enrolled

So, we need to fill in the 3rd premise with a statement that logically asserts the conclusion.

Let’s analyze answer A:

Answer A states that ALL students with learning disabilities have special needs(some students with special needs have learning disabilities), so let’s fill in the missing premise with that.

1) The school needs students with special education needs enrolled.
2) The school has no students with learning disabilities enrolled.
3) ALL students with learning disabilities have special needs.
C)Therefore, the school has no students with special needs enrolled

We can see that the conclusion does not follow from this. The additional premise states that all students with learning disabilities have special needs, this does not exclude the possibility that students without learning disabilities have special needs. So, the school might have students enrolled that need special education that DO NOT have learning disabilities.

Let’s now analyze answer D:

D states that ONLY students with special needs are ones that have learning disabilities (all students with special needs have learning disabilities)

1) The school needs students with special education needs enrolled.
2) The school has no students with learning disabilities enrolled.
3) ALL students with special needs have learning disabilities.
C) Therefore, the school has no students with special needs enrolled

With this premise, we can see that the conclusion does logically follow. ALL students with special needs have learning disabilities (and SOME students with learning disabilities have special needs). So, if you do not have any kids with learning disabilities enrolled, then you can’t have students with special needs enrolled because all students with special needs have learning disabilities.


In diagramming:

A)   Learning disabilities –ALL-> Special needs
Special needs—SOME-> learning disabilities

D)   Special needs –ALL-> Learning disabilities
Learning disabilities –SOME-> special needs