Q10 - Columnist: The failure of bicyclists

[jade.harry1]

I don't understand why C is the right answer here. The conclusion is that "bicyclists are at least PARTIALLY responsible for more than half of the traffic accidents..." So, from that statement, isn't there enough room to imply that there might be more than one factor contributing to a given accident. Because of the columnists' choice of "partially" I just assumed that she had already taken C into account...

[bbirdwell]

This one's all in the math.

The argument says:

1. failure to obey regulations is a factor in more than one quarter of these accidents
2. inadequate safety equipment is a factor in more than one quarter of these accidents

Therefore, the above accounts for more than half.

Is this true? Only if there is no overlap in the two groups. In other words, if all the accidents caused by failure to obey regs were also caused by safety equipment, then the total is still only a quarter overall.

Though of another way, this argument only works if, in each of the above cases, the causal factor mentioned excluded the other causal factor. This is the only way we can add one quarter plus one quarter to get one half.

(C) brings attention to this.

Got it?

[ldagosti]

I'm still confused as to why (B) is incorrect?

[timmydoeslsat]

B is incorrect due to the fact that we are given two causal factors in traffic accidents. Over 25% of them involve bicyclists failing to obey traffic rules. We also know that 25% of them also involve bicyclists using inadequate safety equipment.

We are told, as fact, that the factors are causes in accidents. These are not presented as correlations. The error in the reasoning of the argument is our conclusion stating that over half of traffic accidents are caused by bicycle issues.

The argument does fail to consider that a traffic accident can have multiple causes. This means that it would potentially be in error to combine the percentage amounts. They could be occurring in the same accidents.

[shirando21]

I knew where went wrong was 1/4+1/4=1/2, maybe there's overlap, then the result will be <1/2.

But it was really hard to pick the right expression in a short time.

Now I understand.

[austindyoung]

Chose (B)- see why (C) is correct. However, I didn't see the 2nd part of this statement, "is also a factor" as being the same as the first part "is a causal factor." But I guess I this case they are analogues, which, considering the nit-pickiness of the LSAT, I could easily imagine another problem where it tests you on (what I think could be) an assumption.

[ericha3535]

I chose B for this question as well but realized that flaw was all about this neglecting the "overlapping" accidents:

26% accidents due to failure to comply traffic laws
+
26% accidents due to lack of bicycle's safety features
---
argument concludes: must be responsible over 50%

Now, after giving much of a long thought to this question, I realized that
A is the "necessary assumption" rather than a flaw...
Because negated version of A would say: not less than half of accidents are due to motorists. That means at least, 50% of the accidents are caused by motorists. If this is the case, how the hack would one to conclude that those 2 bicycle related causes constitute over 50% of total accidents?

At the same time, I was like... yeah I know it's necessary assumption and which means that it can't really point out the flaw... but really why isn't it the correct answer?

Because I thought C and A are sort of saying the same thing in a different way.

Then I realize that the argument does not really have to assume or actually assume that motorists cause less than half of 50% of total accidents.

By claiming that those bicycle related causes constitute AT LEAST 50%, the argument never assume that the other half is caused SOLELY by motorists: it could be caused by pedestrians, traffic signal faults, and more.

So, this answer would have been if said: argument presume that other alternative causes other than those 2 bicycle related causes constitute less than 50% of total accidents.

Need your verification people!

[tommywallach]

Hey Guys,

I'm just going to take this one on in total, since we have a lot of mini-discussions going on on different subject. This is a Flaw question, so we start by noticing the core:

Conclusion: B's are at least partially responsible for more than half of traffic accidents involving B's.

Premise: 1) B's failure to obey t.r. is causal factor in more than 1/4 of accidents. 2) Bad B safety is a causal factor in more than 1/4 of accidents.

First off, the word "factor" means a causal factor, so there's no trickery there. Secondly, the flaw here has been discussed to death. There could be overlap between these two groups. Automboiles have NOTHING to do with this argument.

(A) As I just said, cars have nothing to do with this argument. It doesn't matter how many OTHER factors relate to these accidents. If bicycle errors are contributing factors, then our facts are set. In other words, Ericha, I don't see your argument as being a convincing one in this case. No other causes are relevant. The only error in this argument is the overlap.

(B) People are always eager to go to this one, but as Timmy said above, a correlation has to be presented as a correlation (i.e. Last year, there were twice as many cops on the street, and half as much crime). If it's presented as a cause (i.e. Last year, the mayor's decision to double the number of cops on the street caused the crime rate to drop), then there's no causation/correlation error.

(C) CORRECT. This is the flaw. If an accident can have multiple causes, then there could be overlap between the two groups cited in the stimulus.

(D) The facts are presented as facts, so we don't need the source.

(E) Severity is totally out of scope.

Hope that helps!

-t

[alena21century]

I think this one is very confusing. It says in the stimulus that not obeying the law is a casual factor (not the single cause) of a quarter of accidents involving bicycles. Similarly, it says that bad equipment is a factor (not the only cause) in another quarter of such accidents. However, when they did the math and drew the conclusion, they treated each factor is the only cause without allowing them to overlap.

[kyuya]

Discussion of the stimulus:

The stimulus is stating that since over one quarter of bicyclists do not follow traffic regulations, and also over one quarter use inadequate bicycle safety so therefore, they are responsible for over half.

The math here is pretty obvious, but let me make it more clear (more for myself than anything..) slightly over one quarter + slightly over 1 quarter = slightly over half. So what does this mean, in terms of implicit assumptions?

It is assuming there is no crossover between both of these groups. How do we know this? Well, because the math indicates that we are simply adding over one quarter twice for two presumably different groups, without consideration to how they may actually be related by being part of the same group. Its quite possible that both of these groups actually are completely a part of the same group, therefore making both of these groups put together only account for slightly over one quarter of accidents.

Lets check out the answers

(A)

This is wrong.

The author does not claim motorists are not at fault AT ALL for the two things he claims bicyclists are at least partially responsible for; he simply is stating that the people biking share some responsibility as well.

The implication of the latter part of this answer choice "..motorists are a factor in less than half of traffic accidents.." is that they are not in part responsible for the accidents involving the bikers.


(B) It never infers a causal connection from a correlation; lets dig a bit deeper here.

For the first incidents with bikers, we are simply told it IS causal factor - there is not inference from a correlation. Secondly, we are told the second set of incidents involving bikers is "..a factor", but once again, there is no inference drawn.

(C) This is the correct answer.

As discussed in the discussion of the stimulus, the assumption is that these two groups do not over lap. In other words, that more than one factor could not have contributed to a given accident.

(D) This is not an issue here, nothing about sources is spoken about, so a source is insignificant.

(E) Severity of injuries is not important.

I think this question is tricky because the flaw is very easy to see, but the answer choices are pretty tough. Probably a good example of where POE is very valuable.

[CaitlinC257]

I completely understand your reasoning behind the flaw. I thought of the same reasoning while I was reading the stimulus, and I searched for an answer that would account for the math. I STILL, however, DO NOT UNDERSTAND HOW C can be interpreted to be stating that. It doesn't discuss the numbers overlap. It states that the argument does not consider that other factors could lead to the accidents, which it does with the terms "a factor", partially responsible.

This one's all in the math.

The argument says:

1. failure to obey regulations is a factor in more than one quarter of these accidents
2. inadequate safety equipment is a factor in more than one quarter of these accidents

Therefore, the above accounts for more than half.

Is this true? Only if there is no overlap in the two groups. In other words, if all the accidents caused by failure to obey regs were also caused by safety equipment, then the total is still only a quarter overall.

Though of another way, this argument only works if, in each of the above cases, the causal factor mentioned excluded the other causal factor. This is the only way we can add one quarter plus one quarter to get one half.

(C) brings attention to this.

Got it?

[ohthatpatrick]

I think you're reading (C) and hearing
other factors could lead to the bike accidents
which would mean "sometimes a bike accident has nothing to do with ignoring traffic laws or lacking safety equipment. Sometimes a bike accident is caused by something else (like texting while biking)."

But (C) is saying "more than one factor may contribute to a given accident".
Not "more than one factor may cause a certain type of accident".
It's saying "a given bike accident --- one specific bike accident --- may be caused by more than one contributing factor".

So it's saying, "It's possible that some bike accidents are caused by both FAILING TO OBEY REGULATIONS as well as by INADEQUATE SAFETY EQUIPMENT."

If those two factors are sometimes MUTUALLY the cause for a given bike accident, then there is overlap between the two 25% stats.

Hope this helps.

[EllenG551]

Apologies for doubling back on this. I'm still a bit confused about the answer choice C. I understand this is about the possible overlap in the two groups, but I still couldn't figure out how answer choice C addresses this problem. The conclusion suggests "at least partially responsible for", and I assume this allows other factors that may contribute to the accidents.

Thank you in advance!

[ohthatpatrick]

Sorry for the delayed response.

Consider it this way:
If every given bike accident had ONLY ONE CAUSE,
then bike accidents caused by failing to obey traffic rules would be completely separate from bike accidents caused by inadequate safety equipment.

The author's logic would be fine. More than 25% of accidents are caused by X, and more than 25% of accidents are caused by Y, so more than 50% of accidents are caused by X or Y.

If a given bike accident can have MORE THAN ONE CAUSE,
then some bike accidents may be caused BOTH by failure to obey traffic rules and by inadequate safety equipment.

Here the author's logic doesn't work. Let's say 26 of 100 accidents were caused by bikers who broke the traffic rules AND had improper equipment.

The premises would still be true, "more than a quarter of the 100 accidents involved breaking traffic rules and more than a quarter of the 100 accidents involved improper equipment".

But the conclusion would no longer hold. It's not true that "more than 50 of these 100 accidents can be blamed on traffic rules or safety equipment" We only know of 26 that fit that category.

Let me know if that's still confusing.

[YurikaC738]

To interpret C: Two factors may contribute to a given accident (X obey +X safety equipment -> Accidents), thus 25+>25 is not necessarily more than half