#10 - Columnist: The failure of bicyclists to obey traffic

[Jkjones3789]

Hello , SO in this Flaw in the Reasoning question. I didn't pick C because I thought that the author did include two reasons for the accidents and not one ... The failure to obey traffic regulations along with the inadequate bicycle safety. So I went with B because I thought it was more correctly explaining the causation correlation flaw, Please explain why its C in light of the fact that two factors are listed? Thank You

[Lucas Moreau]

Hello, Jkjones,

The columnist is making a mistake about numbers. He is adding up the two 25% accident rates, of failure to obey traffic regulations along with inadequate bicycle safety, to get a 50% rate of accidents for which bicyclists are at least partially responsible. This would only work if every accident had only one of those two causes, and none had both. See?

Here's an example...let's say that we have a city with a population of 1 million people. 75% of the people in the one city own a red car, or 750,000, and 75% of people in that city own a blue car, or 750,000. There aren't 150% of people in this city, or any city for that matter, so it must be true that at least some people in this city own both a red car and a blue car.

Furthermore, in my example, it is also possible that there are people in this city who own neither a red car nor a blue car. It could be true that there are 750,000 people in this city who own both a red car and a blue car, and 250,000 people who own neither a red car nor a blue car.

In the same way, in the question, it could be true that 75% of bicyclists involved in traffic accidents were blameless, and 25% of them had both inadequate bicycle safety and the failure to obey traffic regulations causing them to be partially responsible. So the columnist's argument that half of all bicyclists are partially responsible does not follow from his premises because of his numbers flaw.

Hope that helps,
Lucas Moreau

[Harman]

In the context of the discussion above, doesn't "partially responsible" which is in the conclusion, indicate that there may indeed be more that one cause. Even if the two causal factors (factor 1 and factor 2) in the premises must be mutually exclusive for the conclusion to be valid, can't there still be a 3rd factor or a 4th factor that are not restricted by the exclusivity present between factor 1 and 2.

So you can have factor (1 and 3) and factor (2 and 4)

In this scenario there is no overlap between factor 1 and 2, which is the necessary assumption, but there are still other contributing causal factors, which I believe the statement "partially responsible" allows for.

Also the premises state that factor 1 is "a" causal factor, meaning one out of others./?
So if 25% + accidents = 10 accidents, there could be 3 causes for each one; factor 1 would just have to be 1 of those causes. This would allow for factor 1 to be "a" cause in 25% of accidents, while still not being the only one. And as long as factor 2 was not also one of the 3 causes, the assumption is not violated. Factor 1 is basically taking up a % of each unit that 25% of accidents are composed of.

It seems that the way they worded the premises, and then the word "partially" in the conclusion, was in order to is indicating that factor 1&2, event though mutually exclusive, are not the only possible causes. So to get to AC C you would have to separate what is being said in the conclusion and take the flaw to be the assumption by itself.

In other words, the author is concluding one thing, but what he must assume to get to that conclusion is contradictory to it. So even with the conclusion allowing for other causes, the assumption necessary to get to the 50% eliminates that possibility, hence AC C. Flaw = assumption ? Maybe ("a" causal factor) doesn't mean one out of others?
Is this logic valid?

Thanks/sorry for any grammatical errors - in advance.

[Ricky_Hutchens]

Hey Harman,

The wording does in fact indicate that the listed cause was not the only cause. That is the problem here. Because the cause are not mutually exclusive, you can not add the percentage together because there may be overall between the causes. Whether or not a 3rd or a 4th cause exists is irrelevant.

The author can not validly add the percentages for these two causes together unless he is able to show that all accidents caused by 1 were not also caused by 2. Or vice versa.

Hope that helps.

[Harman]

Thanks for the quick response.

I completely understand that the mutual exclusivity is the flaw.

If AC C was limited to factor 1 and factor 2 then it would make more sense to me. We know that the author belies that there may be other possible causes contributing to the 50% apart from the two factors he talked about in the premises. This is based on the statement that they are at least "partially" responsible for at least 50% of the accidents. 1+2 are present in 50% of accidents. This just means: 1<--/-->2. 1 and 2 can still be with other causes to = 50% with this assumption in play.

Believing factors 1 and 2 cant both happen at the same time together does not mean he believes that 1 and 2 happen alone, there may be other contributing causal factors, which the language in the stimulus suggests is the case. AC C is suggesting that he does believe that they are happening alone with no other contributing causes other that 1 and 2; fails to consider the possibility that more than one factor may contribute to a given accident. The scope of this AC is beyond just adding factor 1 and 2. If he fails to consider "more that one" that means he assumes there is only one cause for a given accident. That is not the same as saying 1<--/-->2. That is saying 1<--/-->2 and only 1 and 2 for the 50%. No where does he explicitly say that 1 and 2 are the only causal factors, and he does not assume it either.

This is the discrepancy I'm trying to work out.

[Harman]

In other words:

AC C is stating that he believes that there is only one cause per accident.

His assumption is that failing to obey traffic regulations (cause 1) and inadequate safety equipment (cause 2) are not present together as causal contributors to the effect/accidents.

His assumption is not the same as the AC. This is a first family Q type, wouldn't AC C fail the fact test; he never says only one cause per accident. Only that cause 1 and cause 2 can't happen together. 1 and 2 being mutually exclusive does not stop 1 or 2 from happening in conjunction with other causal factors to create accidents. That is what I meant by 10 accidents = 25% and factor 1 being just 1 cause in each of those ten accidents. Just because factor 2 is not present with factor 1 does not mean there can't be a different cause there with factor 1. AC C is saying that 1 must be alone.

Hopefully this is a little easier to understand than my post above.

[Emily Haney-Caron]

Hi Harman,

Answer choice C could be worded better. Unfortunately, it isn't. However, you aren't looking for the perfect answer; you're looking for the best answer of the choices you are given. This is a question where a pre-phrase is really, really helpful - if you go to the answer choices already knowing what you're looking for, you're unlikely to be thrown off by the fact that the wording of C could be a bit more clear; it is clearly the closest/best answer. Hope that helps!

[Harman]

I had the pre-phrase,and I was able to eliminate all of the other answer choices, I wanted to know if I had the correct logic, or if I was missing something important, since I had a bad feeling with AC C.

Now that I think of it, since this is a Flaw question, the CR will have abstract language, and even though the CR could be taking about all other possible causes, the assumption of exclusivity still fits into the language presented in AC C. So even though this AC can apply to a broader range of unnecessary assumptions, it is still better, since the necessary assumption can fall under that umbrella, whereas in the other AC, the assumption does not fit at all.

Thanks, that works.

[LAM]

This thread was really good because I was stuck on the exact problem Harman was. I was thinking exactly like Harman in justifying for not choosing the correct answer, but it helped me to substitute 'partially responsible' and ' "a" causal factor' with at least one. So I read it like this, ' the failure of bicyclists to obey traffic regs is at least one causal factor...' and 'bicyclists are at least one causal factor for more than half of the traffic accidents...' This for some reason helped me immensely to see the light so to speak. I imagined a pie chart with 30% (more than a quarter) attributed to traffic violations being ONE of the reasons for those accidents and then another 30% OVERLAPPING the first third I shaded in. This third was marked for faulty equipment or idiot bicyclists not wearing their helmets. Some of those who didn't wear their helmets ALSO violated a traffic reg (didn't yield or something). So, this accounts for some overlapping (whereas others just ran a red light, but were wearing their helmet etc - they only screwed up in one category.) Now, with this overlap in mind, it is true that it can be said that bicyclists were AT LEAST one causal factor in the 2 shaded sections of the pie chart. But they are overlapping a lot so let's say these 2 sections do NOT make up 50% - in fact they overlap so much they only make up 40% of the whole chart. Now with 60% of the chart is still not colored in - these traffic accidents involving bikes could just be because in that town the motorists have no respect for bicyclists and mow them down. Who knows. We don't know what caused the other 60% of accidents - for all we know bicyclists could not have even been one causal factor. They were perfect riders. Answer C says 'fails to consider the possibility that more than one factor may contribute TO A GIVEN ACCIDENT'. The answer choice is not necessarily talking about the two pie slices I mentioned earlier - it is talking about the set of all the accidents we are discussing - the whole pie chart - the total of accidents involving bicyclists. The stimulus accounted for the possibility of more than one causal factor in the 2 pie slices - the subsets but not for all the accidents. In fact it doesn't even discuss the other accidents causes - it just makes a claim that 50% of the pie chart must be filled in - in other words there is no overlap. Once I realized this, the light bulb went on. I only write all of this because my train of thought is not as heady as Harman's. Perhaps, my simpleton version (ha! - that's what I need to understand this stuff!) may be of help to someone else stuck on this. Reflecting, I think there could have been better answer choices; frankly this one seemed asinine. It seems that it should have been worded, 'fails to consider any possibility for other factors that contribute to accidents'. Correct me if I am wrong on any of this. Writing this out helped me and may help someone else.

[Adam Tyson]

Hey again LAM! The language in the correct answer about "a given accident" is just another way of saying that there could be overlap, that one particular accident could have multiple causal factors involved. If any one given accident, picked at random out of all the accidents, could have more than one causal factor, like ignoring regulations and inadequate equipment, then the two groups could, as you said, overlap. Maybe they overlap completely, and bicyclists are partially responsible only for those accidents making up more than, but not necessarily much more than, 25%. We don't need to imagine additional causal factors, but only to recognize that the two factors given could overlap and therefore should not be simply added together. We cannot prove anything about "more than half", only about "more than 25%".

The same error appears here: half of the sandwiches I made this week had meat in them and half had cheese in them, so therefore all of the sandwiches I made had either meat or cheese in them. Maybe half the sandwiches had meat AND cheese, and the other half were all PB&J!

Straight up numbers and percentages here, folks, and no need to complicate things further with other causal factors not mentioned in the stimulus. Stick to what they gave you and deal with it on its face, and the test will go faster, easier, and with more correct answers.

Good luck, keep up the good work!