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#19 - Train service suffers when a railroad combines

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akanshachandra
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Hello! I do not understand why C is correct. I chose D, because I thought that it successfully followed the argument that for the railroad to be successful it must concentrate exclusively on one of the two markets: freight or commuter, and D does just that. Though I was stuck between C and D, I thought D was the better answer.
Adam Tyson
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Try diagramming the conditional relationships here, akanshachandra, and things will become clear. In the stimulus, we have these relationships:

Premise: If CC&F (combine commuter and freight) :arrow: SS (service suffers)

Conclusion: SR (successful railroad) :arrow: CC&F (don't combine - do just one)

How do we get to the conclusion that you should not combine? Use the contrapositive of the first claim:

SS :arrow: CC&F

(if your service does not suffer, it proves that you did not combine commuter and freight services)

Link that contrapositive to the conclusion:

SR :arrow: SS

This is your prephrase of the missing link, which the author must have assumed: If you are a successful railroad, your service does not suffer. Now you can put the whole thing together and you get this conditional chain, which gets you to your conclusion nicely:

SR :arrow: SS :arrow: CC&F

Answer C matches this prephrase, and that's why it is correct. Using the "Unless Equation", answer C makes serving customers well (which is like saying service does not suffer) a necessary condition, and being a successful railroad business is sufficient, which is what we just diagrammed as our missing link!

Answer D could be diagrammed this way:

CC&F :arrow: SR

(Saying that they concentrate just on commuter service is one way of saying they do not combine commuter and freight, right?) This is a mistaken reversal of the conclusion, meaning that it simply reversed the order of the terms without also negating them. Our author definitely did not assume this, nor is this mistaken reversal helpful in establishing our conclusion because it's backwards. Beware these reversals, as well as their ugly cousin, the mistaken negation (where you only negate the terms but leave them in their original order, which is bad logic).

Keep working on your conditional statement diagrams, and practice drawing them all out until you get so good at them that you no longer have to draw them to see them clearly in your mind. Be careful, and when in doubt, draw it out!
Adam M. Tyson
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hassan66
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I got this correct by doing a process of elimination.

A) irrelevant
B) One of my prephrases was that the railroad even cares about being a successful business. And this made me pause, but ultimately the phrase "first priority" seemed exaggerated.
C) --
D) It must concentrate on one or the other, doesn't matter which so I eliminated this one
E) irrelevant, the author references the railroad, not the consumers

It is okay to not diagram the conditional logic? They mentioned service and being a good business, so I figured C was correct as a way of linking the two but it was more so because I knew the others had to be incorrect.
Adam Tyson
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Perfect, hasan66! That "mechanistic" approach, similar to what you might do in a Justify the Conclusion question, works equally well on many "supporter assumption" questions like this one. You saw an obvious gap in the argument between "serving customers well" and "successful business" and looked for something to bridge that gap. Great work, that's the way to do it!

We can use the conditional diagrams to help understand where the gap is, and that's a great tool to know how to use when and if you need it, but it's not something that you MUST do in order to attack this question or others like it. If you can take the more intuitive and mechanical approach that you used, and do so with confidence, you'll find that a lot of questions like this one, as well as many strengthen and justify questions, go quickly and easily. Occasionally you will have two contenders that seem to bridge the gap, and then you might need to try the Negation Technique or use conditional diagramming to help choose between them, but getting the answers sorted out this way is still a great start.
Adam M. Tyson
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