A study of 8,000 randomly chosen adults in a European country

Question

A study of 8,000 randomly chosen adults in a European country found that 75 percent of those who consumed alcohol an average of twice or more per week over a six month period suffered at least one cold during that period. We can tentatively conclude from this that consuming alcohol tends to increase one’s susceptibility to colds.

Which one of the following, if true, would most weaken the argument?

(A) Eighty percent of those in the study who
consumed alcohol three times or more per week
suffered colds over the six-month period.
(B) Seventy-five percent of those in the study who never consumed alcohol suffered at least one cold over the six-month period.
(C) Fifty percent of those in the study who consumed alcohol an average of once per week suffered colds over the six-month period.
(D) Less than 75 percent of those in the study who suffered colds over the six-month period consumed alcohol an average of once per week or more.
(E) Sixty percent of those in the study who did not suffer any colds over the six-month period consumed alcohol once per week or more.

GMATNinja · Accepted Answer

For (E), the percentage of people in the study who consumed alcohol is pretty important.

If alcohol-drinkers make up 90% of those in the study but only 60% of those that never got a cold, then it seems like consuming alcohol increases the likelihood of getting a cold. On the other hand, if alcohol-drinkers make up 10% of those in the study but 60% of those that never got a cold, then it seems that consuming alcohol decreases the likelihood of getting a cold.

Because we don't know what percent of people in the study consumed alcohol, (E) doesn't weaken or strengthen the argument, and we can eliminate it.

With (B), the idea is that if 75% of those who did NOT consume alcohol got a cold AND 75% of those that DID consume alcohol got a cold, then alcohol consumption does NOT increase the likelihood of getting a cold. It doesn't necessarily  disprove  the idea that alcohol consumption COULD increase one's susceptibility to colds, but it definitely WEAKENS the idea.

For that reason, (B) is the best answer choice.

I hope that helps!

nithyak · Answer

How is B better than E?

The conclusion correlates alcohol consumption with increased susceptibility to cold.
Choice B says seventy five percent of those in the study who did not consume alcohol had cold episodes. This could simply mean that there might be other factors other than alcohol consumption that could have caused cold. Still doesn't rule out that alcohol consumption increases susceptibility to cold.

Choice E says sixty percent of those who never got cold were in fact consumers of alcohol. This points directly to the fact that in spite of drinking alcohol, people did not suffer cold episodes. So definitely a better choice in my opinion.

GMATNinja  pls help me understand if there is a flaw in my reasoning.

unraveled · Answer

A study of 8,000 randomly chosen adults in a European country found that 75 percent of those who consumed alcohol an average of twice or more per week over a six month period suffered at least one cold during that period. We can tentatively conclude from this that consuming alcohol tends to increase one’s susceptibility to colds.

Which one of the following, if true, would most weaken the argument?

(A) Eighty percent of those in the study who consumed alcohol three times or more per week suffered colds over the six-month period. - WRONG. Nothing as such is suggested. It doesn't helps us to know whether susceptibility is increased. It just makes similar statement with bigger numbers/scale.
(B) Seventy-five percent of those in the study  who never consumed alcohol suffered at least one cold  over the six-month period. - CORRECT. 
(C) Fifty percent of those in the study who consumed alcohol an average of once per week suffered colds over the six-month period. - WRONG. More or less same as A.
(D) Less than 75 percent of those in the study who suffered colds over the six-month period consumed alcohol an average of once per week or more. - WRONG. Less than 70% could be 10% or 70% also. No clarity.
(E) Sixty percent of those in the study  who did not suffer any colds  over the six-month period consumed alcohol once per week or more. - WRONG. This category of people is not concerned at all. It doesn't helps us to know whether susceptibility is increased.

Answer B.

KittyDoodles · Answer

Hi  GMATNinja ,

Please can you further explain the below

If alcohol-drinkers make up 90% of those in the study but only 60% of those that never got a cold, then it seems like consuming alcohol increases the likelihood of getting a cold. On the other hand, if alcohol-drinkers make up 10% of those in the study but 60% of those that never got a cold, then it seems that consuming alcohol decreases the likelihood of getting a cold

Thanks

GMATNinja · Answer

The logic here is a bit tricky!

Let's say that in the study there are only 12 alcohol-drinkers, compared to a  huge  number of non-drinkers. From the passage, we know that 9 of the drinkers got a cold, and 3 did not.

(E) tells us that these 3 healthy drinkers account for 60% of the people who didn't get sick --  which means that only 2 other people in the study didn't get a cold.

So, in our huge group of non-drinkers, the vast majority DID get colds. All of them but 2 people got sick!

In this case, it seems like drinking alcohol actually  protects  you from getting sick.

But what if we flip the proportions?  Suppose that a large number of people in the study drink, and only a small number don't drink. If 25% of the drinkers won't get sick, that's a pretty large number of people.

According to (E), this chunk accounts for 60% of the total people who won't get sick. The other 40% of people who won't get sick comes from the non-drinkers. This 40% group is obviously a  bit  smaller than the 60% chunk, but we're pulling the 40% chunk from the  much smaller  group of non-drinkers.

So, it could be that  almost everyone in the  non -drinking group doesn't get sick .

With these proportions, it seems like drinking alcohol  increases  your susceptibility to getting sick.

Because we don't know the composition of the people in the study, we can't say that (E) weakens the argument.

I hope that helps!

agrasan · Answer

Hi  IanStewart   KarishmaB   DmitryFarber

Just wanted to confirm reasoning for (E), can we say that what option (E) says is expected because the argument never said that all people who drink will get cold? The argument just said that the drinking alcohol increases likelihood of getting cold. Overall, (E) doesn't provide us much info to weaken the conclusion.

bb · Answer

E talks about people who did not get a cold. It is not giving us any new details. We already know that 75% got a cold so it is talking about the 25% who did not and it’s not giving us any new information.

You can see that Jim at Ninja is explaining this answer is pretty well in the second post.

PS. Unfortunately I’m not following your reasoning and I can’t confirm that that’s the reason to eliminate it.

WhitEngagePrep · Answer

I think one of the things missing from the explanations above is a bit more of a discussion around the structure of the argument itself. This argument is utilizing two common Critical Reasoning structures, and each of these common structures have very specific questions we should be asking when we see them show up! So let's look at each structure and see how it shows up in this argument. In this argument, the claim is that drinking causes the colds. But what if it's the other way around? Could getting a cold make you drink more? Or what if there is something else causing the drinking and the colds? Or maybe this is just random chance. So the first question I might ask here is "are the drinkers and non-drinkers of 2+ times a week actually the same in every other way? Is there any other reason why one group might get colds more than the other. However, there is an added element missing from this argument - it doesn't say that the group that drinks is getting MORE colds than the group that doesn't. It just says they suffered at least one cold during the period. But what if a similar fraction also suffered at least one cold. Or worse, what if the non-drinkers suffered 3+ colds during that period. The better conclusion might be that drinking actually helps PREVENT a cold! So I take all of this together to confront the answer choices: - is the direction of causation correct, could it be backwards or something else? - are drinks 2+ vs non actually comparable? - is the incidence of colds actually worse for drinks 2+ vs not? (A) Eighty percent of those in the study who consumed alcohol three times or more per week suffered colds over the six-month period. Seems to follow the story that more alcohol = increased incidence of colds. So if it does anything, it supports the argument. (B) Seventy-five percent of those in the study who never consumed alcohol suffered at least one cold over the six-month period. Hold on, let's check the passage, did it forget to mention what was happening to the non-drinkers in terms of getting colds?? It didn't - we just heard that folks drinking 2+ a week were getting colds, but they didn't mention if that was more or even different from folks who had under 2. If the folks drinking under 2 drinks were also getting colds at similarly high %s, then these groups aren't experiencing different outcomes so it would almost seem like drinking had zero impact on colds. This is definitely going to undermine the argument! (C) Fifty percent of those in the study who consumed alcohol an average of once per week suffered colds over the six-month period. Seems to follow the story that less alcohol = lower incidence of colds. So if it does anything, it supports the argument. (D) Less than 75 percent of those in the study who suffered colds over the six-month period consumed alcohol an average of once per week or more. This math can be a bit confusing. Up to now, we've been slicing the group based on how much they drank and then considering their colds for each group. This choice slices the group based on colds and then considers their drinking status. So if 100 people in the study had colds, under 75 of them consumed alcohol an average of 1+ times a week. But that's a huge range, and depending on where in that range the number landed, this would be a different story potentially. If 74 of the 100 consumed alcohol an average of 1+ times a week, then only 26 consumed alcohol under once a week. So a larger proportion of cold-havers were "drinkers" which would support the story. But 1 is also less than 75 percent. So what if 1 of the 100 people who got colds drank 1+ drinks, then 99 of the cold havers would be low drinkers. This would definitely weaken the story. But we don't know which it is, so we must eliminate! (E) Sixty percent of those in the study who did not suffer any colds over the six-month period consumed alcohol once per week or more. Again, confusing math as it divides the group in ways we haven't before. Now, we're looking at the people who magically escaped getting a cold. So let's pretend that 100 people in the study never got a cold. 60 of them consumed alcohol 1+ times a week, meaning that 40 consumed alcohol under 1 time a week. This might imply that the more you drink, the less likely you are to get a cold (same as before), but it leaves open the same problem as the argument. We have no clue what the breakdown is for folks who did get a cold. What about the people who did get colds, if the % of cold-havers was higher for alcohol-drinkers, then we might still be able to argue that alcohol could increase incidence of colds. But if the % of cold-havers was lower or the same for alcohol-drinkers, then we could see the trend towards weakening. However, B has done a better job of weakening all on its own, and doesn't need more info like this choice would. So we should eliminate at least in favor of B! Hope this helps!

Whit

A study of 8,000 randomly chosen adults in a European country

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A study of 8,000 randomly chosen adults in a European country

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