Question: Bicycle Helmets

Comment on Bicycle Helmets

What is the difference the less than 20% and 80% which was stated in the text? I couldn't differentiate these sentences
gmat-admin's picture

Good question.

The 80% in the passage refers to the 1000 VICTIMS (dead people), whereas the 20% in answer choice C refers to CYCLISTS INVOLVED IN ACCIDENTS (accidents in which some cyclists died and some cyclists survived).

As per accident reports, 80% victims were not wearing a helmet, that means the 20% that were wearing helmet died despite wearing it. This indicates that there may be other confounding factors such as catastrophic accidents...

Why not answer choice E?
Regarding choice E, it is a well known fact that road accidents cause injuries and sometimes severe injuries cause deaths.
Most cyclists in choice E indicate that they were able to avoid worse injuries by wearing a helmet.
After all, cyclists involved in accidents don't die of disease such as cholera. Cyclists involved in accidents die because of injuries, be that head injury or torso injury.

The representative's argument is flawed and uses statistics which will not survive a simple hypothesis test (considering that 20% of those who died were wearing a helmet).

What do you think?
gmat-admin's picture

You've made a really good point. However, since the conclusion is about dying, the best answer will be one that addresses dying versus one that discusses severity of injury.

Hi Brent
C doesn't say anything about dying either.
What do you think?
gmat-admin's picture

I should have clarified that my comment above was related to why answer choice E is incorrect (because it introduces the notion of SEVERITY of the accident, when the conclusion is about DYING from the accident).

On the other hand, answer choice C builds on the fact that 80% of the cyclist who died were not wearing a helmet.

Hi Brent,

Could you explain in another way why C is the correct answer and how can I eliminate E? I'm not convinced that C is the correct answer.

gmat-admin's picture

I'll try.

First keep in mind that a person who DIES in an accident is different from a person who is INVOLVED IN an accident.

Now let's imagine a situation in which 80% the people INVOLVED in accidents were wearing green socks.

If wearing green socks has no effect on whether or not a person DIES in an accident, then we'd expect that 80% of the people who DIED will be wearing green socks.

Conversely, if ALL of the who died were wearing green socks, then it would seem that wearing green socks seems to drastically increase the chances of dying.

On the other hand, if NONE of the people who died were wearing green socks, then it would seem that wearing green socks seems to drastically decrease the chances of dying.

Do, to determine whether wearing green socks helps prevent people from dying, we must take the percentage of people involved in an accident who were wearing green socks and compare it to the percentage of those who DIED that were wearing green socks.

Now change "green socks" to "helmet."

In order for helmets to help DECREASE the chances of dying in an accident, it must be the case that MORE than 20% of the people INVOLVED in an accident were wearing a helmet at the time. IF it were the case that 20% of the people INVOLVED in an accident were wearing a helmet at the time, then we'd have to conclude that wearing a helmet does not reduce the death rate. So, answer choice C is VERY IMPORTANT information.

In answer choice E, we're talking about severity vs dying. Since the conclusion is all about dying in an accident, this answer choice is already a little off the mark. That's the MAIN issue. Another issue with E is that it's purely anecdotal. It the BELIEF of those wearing helmets.

I'm having the exact same problems with this question.. I restated C like this: 80% or more were wearing a helmet while involved in an accident (living or dead) thus inconclusive whether it strengthens or not. Or does being involved equate to survived and injured?
gmat-admin's picture

It's a very tricky question.

Your restatement of answer choice C is correct: 80% or more were wearing a helmet while involved in an accident (living or dead)

This definitely strengthens the conclusion. Here's why:

Let's say, for example, that 90% of the people in accidents (living or dead) were wearing a helmet at the time of their accident. IF it were the case that helmets have NO EFFECT, then 90% of the people who DIED would have been wearing helmets.

However, the question tells us that only 20% of the people who DIED were wearing helmets.

This suggests that the helmets must play a role in the apparent reduction of deaths.

Does that help?


I tried to reason as follows
Less than 20% who were in an accident were not wearing helmet. This means that they are a minority when it comes to cyclists in accidents. However 80% of people who died in accidents were not wearing helmet. So,they are a majority when it comes to dying in accident. Off a small number of cyclists not wearing helmet, majority died. This definitely strengthens the argument that wearing helmet reduces death in an accident. Answer is C
gmat-admin's picture

Perfectly reasoned!!

I still don't understand how C is the correct answer despite reading all the comments.
gmat-admin's picture

Try to avoid getting bogged down on one question.
This one is pretty convoluted, so I wouldn't worry about if I were you.

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