Q17 - On average, city bus drivers

[shaynfernandez]

Even after a few reviews of this question I can see why (C) would be the correct answer, but I am having a hard time seeing why (A) would not be the correct answer.

[demetri.blaisdell]

Match the flaw questions can be a slog. First step: find the flaw! The argument core looks like this:

On average, new system is faster --> Fastest person (Millicent) must be using the new system

The flaw here is in using the average to determine an individual case. Quick analogy: The students of Room 10 have the highest average height --> the tallest person in the school is in Room 10. But wait! Couldn't the tallest person be in a different class full of exceptionally short kids? We can't use the average in this way. (C) reverses the order of the elements (no problem here), but has the same flaw. On average, the tomatoes from the experimental plot are larger, so the largest must be from there. What if another batch had one freak tomato?

(A) is not flawed! If every truck bought after 1988 is larger than any before, the largest truck would have to be part of the post-1988 batch.

(B) is flawed, but in not quite the same way. Above, we were assigning the fastest person to the faster (on average) group. Here we are saying Henri is a member of the taller group, so he must be taller than most of the members of the other, shorter group.

(D) is deeply flawed, but does not relate to the argument core above. The conclusion is that the storm was average. That alone should knock it out.

(E) is also flawed but different. Here we have the flaw: A needs less maintenance than B --> B needs a lot of maintenance. The flaw is they could both need very little maintenance. Very different our bus argument core above.

Hope this helps. Let me know if you have any questions.

Demetri

[WaltGrace1983]

The explanation above is sufficient but I took a lot of time going between (A) and (C) and ultimately missed this one yesterday (drilling parallel flaws after a long day of studying might be a recipe for disaster) so, if you'll humor me, I'll put this one in my own words for my own benefit. Maybe it will help someone else too!

On average, new method = faster
Smith is the fastest
⊢ Smith must be using new method

There is a lot of interesting things going on here. Let's see if we can break it down.

(1) Puzzle ≠ Piece Flaw: the argument is concluding something about a specific person from a evidence focused only on an average. We accept that the new method is, on average, faster. However, should we accept that the person having the best speed is using the new method? Absolutely not! Maybe Smith is just super fast with the old method or maybe Smith's group (those who use the old system) is oddly slow. The point is that we cannot really infer something about the piece from something merely about the puzzle.

(2) Sufficient/Necessary Condition Swap: the argument doesn't really lend itself to conditional language because we are just talking about averages here but I think you might also be able to think about the problem very loosely in terms of how conditionals work. We know that (most) new method → faster but we cannot really conclude anything about those who are faster. As I said, this kind of goes back to #1 but it might just be a different way of thinking about it: just because someone satisfies the "faster" part doesn't mean someone satisfies the "new method" part. I hope that makes sense.

We could probably just think about it in terms of the puzzle/piece flaw and move on.

(A) I got tricked! The key to understanding this answer choice is fully understanding what it is exactly saying. It says "All the city's solid-waste collection post-1988 are bigger than all pre-1988." So if this vehicle is the biggest, then it absolutely MUST be the case that it is post-1988 because we know that all pre-1988 are smaller than all post-1988.

CORRECTION: "The city's vehicles post-1988 have, on average, a larger capacity than pre-1988. This vehicle has the largest capacity, so it must have been post-1988."

This correction would be a correct answer that matches the original flaw. Thus, you can really see how the "all" and "any" in the original answer choice makes all the difference in the world.

(B) Depending on the use of the word "generally," I think this one might swing between flaw and not-flawed. If "generally" means "on average" than this argument would be flawed; if "generally" means "most players" than this argument doesn't appear flawed.

This one is very close but is ultimately lacking the original structure. (B) is saying that the blue team is "generally" taller than the gold team, Henri is on the blue team, thus he is taller than most of the members on the gold team. The structural bit that (B) is lacking is that it doesn't attribute Henri to being the adjective. Instead, it attributes Henri to the group the adjective describes. In the original argument, we have a group (new method) and an adjective (faster). It goes on to say (faster) and concludes (new method). However, (B) doesn't do this. We need some information in the premises about Henri being the tallest (or even taller than most might work).

CORRECTION: "The soccer players on the blue team are generally taller than the players on the gold team. Since Henri is the tallest/taller than most, he must be on the blue team."

(C) This is correct! This matches both in structure and flaw because it shows the following...

Experimental plot = largest on average
Largest
⊢ Experimental plot

It shows the perfect puzzle/piece flaw AND it uses the correct kind of premise. Notice how, unlike (B), this uses the largest adjective as the evidence for the claim, NOT the experimental plot group as evidence for the claim. This is a crucial distinction and this is why I was very loosely thinking about this stimulus in terms of the left side and right side of the arrow.

(D) I don't even know where to start with this one. It has absolutely NO relevance whatsoever but the point of review is to understand the arguments for more than just the question they are given in. This argument says the following...

Toronto snowstorm = Heavier than Miami snowstorm
This storm was heavier than any Miami snowstorm
⊢ This storm in Toronto = average

I think I have shown that argument correctly. This almost looks like a false dilemma fallacy but it is so badly flawed it is really hard to say (sometimes the most flawed arguments are ones I have the hardest time really understanding because they suck so bad). So we know this snowstorm is heavier than Miami and all of Miami storms are lighter than Toronto. This one is heavier than Miami so it must be average for Toronto? Couldn't it have been still below average? Way above average? All we did was rule out one possibility (we know its ~average for Miami) but we have NO evidence for what is actually average in Toronto nor do we know how much snow fell at all. This argument absolutely sucks.

(E) This is a relative ≠ absolute flaw. We know that gasoline = more maintenance than electricity. However, we have no basis to say that gasoline = a lot of maintenance.

Here is an analogous example:
Yao Ming is a billion feet tall, I am shorter than Yao Ming, therefore I am short.