Q19 - Train service suffers when

[agersh144]

Can someone please diagram this out for me?

This is my attempt:

Dividing attention > /GFS (not good freight service) & /(Not good commuter service)

_____________________

Conclusion: SB (Succ Biz). > Concentrate on One

What's the missing assumption here?

The correct answer says Unless a railroad serves its customers well, it will not be a successful business.

Unless means negate sufficient so:

/GFS & /GCS > /SB or CP: SB > GCS or GFS

I'm having trouble connecting the dots here, please explain.

[ohthatpatrick]

I think your attempt to diagram the argument was actually pretty well-done, but it illustrates why it's actually NOT helpful to diagram most arguments.

I would not have thought to diagram this one, and I'M actually pretty trigger-happy when it comes to diagramming.

I don't see any conditional triggers in the evidence. Even though we COULD represent those first two sentences conditionally, the lack of conditional triggers makes me think that LSAT is not testing me on conditional logic here.

Furthermore, this is a Necessary Assumption question (the argument "must" make which assumption), and in general I don't diagram Necessary Assumption.

After all, our task here isn't to prove the conclusion. I diagram mostly for Inference (Must be True), Sufficient Assumption, and Principle Justify, because there we are actually trying to prove an idea.

Since you asked, though, he's how I would attempt to diagram it.

Prem:
Dividing attention --> ~(serve customers well)

Choice (C):
~(serve customers well) --> ~(Successful Biz)

Those two chain together to give us:
Divide attention --> ~(serve customers well) -> ~(Succ Biz)

The contrapositive of that is:
Succ Biz --> serve customers well --> ~(Divide Attention)

The conclusion says:
Succ Biz --> ~(Divide Attention)

Notice that I'm very careful about not introducing new variables like "concentrate exclusively on one" ... that would make diagramming harder to see, in terms of links.

We need to see "concentrating exclusively" as NOT-dividing-its-attention.

====the non-diagramming way======
Argument Core:

Prem :
When a train service does both commuter and freight service, it serves neither customer particularly well.

Conc:
If a train service wants to be successful, it must concentrate exclusively on one.

If you were trying to do this problem without diagramming, I hope that when you reach the conclusion you would notice the "new guy" ... i.e., successful business?

The correct answer is going to have to define what's required of a "successful business", because that's what the conclusion is claiming and the author never gave us any rules/definitions of "successful business".

So just a quick scan eliminates (A) and (E), since they don't address the "new guy".

Why does the author think the current way ISN'T a successful business --- the only thing that sounds like a negative about the current way is that the railroad doesn't serve either customer base particularly well.

So that's the gap we need to connect: "not serving your customers well" and "not being a successful business".

(A) "little in common" is too extreme ... they could be very similar but still stretch a business too thin to treat customers well

(B) "first priority" is too extreme ... the first priority could be "don't kill any passengers" but this argument would still make sense.

(D) Not only does this arbitrarily pick commuter rather than freight, it also shifts from saying "picking one of the two" is NECESSARY to success to "picking one of the two" is SUFFICIENT for success.

(E) "rarely" is too extreme ... it wouldn't matter if commuters frequently wanted freight service also, it could still be true that a railroad does a poor job of both and thereby frustrates the same customer twice.

Hope this helps.

[agersh144]

Your explanation makes so much sense, thank you for being so thorough and breaking it all down -- really appreciate it!