CR: Animal induced allergies

[ShashankB122]

Source GMATPrep

People who have spent a lot of time in contact with animals often develop animal-induced allergies, some of them quite serious. In a survey of current employees in major zoos, about 30 percent had animal-induced allergies. Based on this sample, experts conclude that among members of the general population who have spent a similarly large amount of time in close contact with animals, the percentage with animal-induced allergies is not 30 percent but substantially more.
Which of the following, if true, provides the strongest grounds for the experts’ conclusion?

A. A zoo employee who develops a serious animal-induced allergy is very likely to switch to some other occupation.
B. A zoo employee is more likely than a person in the general population to keep one or more animal pets at home
C. The percentage of the general population whose level of exposure to animals matches that of a zoo employee is quite small.
D. Exposure to domestic pets is, on the whole, less likely to cause animal induced allergy than exposure to many of the animals kept in zoos.
E. Zoo employees seldom wear protective gear when they handle animals in their care.

OA: A

I am not able to figure out this.

Reasoning:-
Zoo scenerio:
Total Zoo employees who had contact with animals = 1000
Total no of deceased employees = 300
General population:
Total population who have contact with animals = 40,000
Conclusion:- Deceased ppl must be higher than 30 % i.e. more than 40000*0.3 = 12,000

Reason: As per choice A:
A zoo employee who develops a serious animal-induced allergy is very likely to switch to some other occupation.
Even if 300 employees who contacted allergies enter normal population pool, the percentage will not change substantially since pool itself is too big.

So how is my reasoning incorrect?

[RonPurewal]

Even if 300 employees who contacted allergies enter normal population pool, the percentage will not change substantially since pool itself is too big.

^^ no, but the percent of allergy sufferers among zoo employees would drop precipitously.

the point is that, if there were no correlation to the zoo job, then the percentage would be the same. (e.g., if 30 percent of men are over six feet tall, then it's a safe bet that about 30 percent of male zoo employees are over six feet tall, too.) so, if there's a selection effect against this job for a particular group, then there will be a differential.

[RonPurewal]

also... if you're plugging actual numbers into a CR problem, that's not good.

the point is to think VERY GENERALLY about what the numbers represent, not to fixate on one particular set of values. (worse, more often than not, people try to "plug in" values that are statistical outliers, further exacerbating the problem.)

if there's ever a problem on which "plugging numbers" will actually help, you know where you'll find that, right? it will be in the quant section, with all the other problems on which actual numbers are important.

[AbhijeetS317]

Dear Ron,

Does it mean, that a zoo employee who develops a serious animal-induced allergy is very likely to switch to some other occupation and become a part of the general population? And in this process, he would add up to the number of people who are supposed to be already suffering from animal-induced allergies?

Is my reasoning correct?

[RonPurewal]

that's the point, yes.

(technically, the zoo employees are also included in 'the general population'—so that, when they quit their zoo jobs, they drop out of the zoo population but remain in the general population. but, since zoo employees are such a tiny fraction of 'people in general' (= common-sense observation), it really doesn't matter whether they are included or excluded.)

[YuY283]

that's the point, yes.

(technically, the zoo employees are also included in 'the general population'—so that, when they quit their zoo jobs, they drop out of the zoo population but remain in the general population. but, since zoo employees are such a tiny fraction of 'people in general' (= common-sense observation), it really doesn't matter whether they are included or excluded.)

Hi Ron,

I don't quite understand this explanation. when the zoo employees switch to other occupations, they HAVE NOT spend large amount of time with animals, so the number of these zoo employees should not be added up to the original number of people who have animal-induced allergy because they have spent large amount of time with animals.

The stimulus says the experts conclude among the members of the general population WHO HAVE SPENT a similarly large amount of time in close contact with animals. So the number of zoo employees who swift their jobs should not influence the percentage mentioned in the stimulus because these zoo employees have not spent time with animals.

Thanks for your answering,

[RonPurewal]

because these zoo employees have not spent time with animals.

^^ no.

1/
common sense:
they worked at a zoo.
so... they were around animals a lot.

2/
think about the word 'similarly' in 'people who have spent a similarly large amount of time'.
... similar to whom?
... well, to the zoo employees.

[YuY283]

because these zoo employees have not spent time with animals.

^^ no.

1/
common sense:
they worked at a zoo.
so... they were around animals a lot.

2/
think about the word 'similarly' in 'people who have spent a similarly large amount of time'.
... similar to whom?
... well, to the zoo employees.

But they have switched to other jobs, so they do not spend time with the animals any longer, right?

[RonPurewal]

once you have done something, you will ALWAYS be 'someone who has done' that thing.

[NitinG177]

Hello Ron,

My thought process for picking A is this :

As the zoo employee is more likely to switch jobs, after the disease - from this we can safely say that he HAS an option to evade from the occupational hazard.

The general population that has similar relations with the animals , obviously do not spend time with animals under some occupational obligation .( may be just out of animal love....)

So even if the workers switch their jobs, this is not a possibility with the general population .

Moreover, since the zoo population is so small as compared to the total population ( as mentioned by you), even if the zoo employees leave ( and they will still be a part of the general population) their job, this would not really shoot up the the percent of the total allergy induced general population ( unless of course this process goes on for a long long time).

Please let me know how concrete is this line of reasoning .

Thanks,
Nitin

[RonPurewal]

i think there are ... too many words there. (for instance, the whole thing about 'why do random people spend time with animals?' is irrelevant.)

just make an analogy if necessary.

analogy:
• a factory has big machines.
• these machines are designed for right-handed operators.
• thus, left-handed operators are likely to be injured or even killed by the machines.

ok.

now let's say that 10 percent of the operators are left-handed.

you can bet $$$ that this means WAY more than 10 percent of the overall population is left-handed—because the left-handers are going to avoid these jobs (and/or quit them) if at all possible!

same thing with the zoo problem. but, since death/serious injury is much more dramatic than allergies, it's probably easier to think about.

[NL]

An interesting CR!

I think the main reasoning is that the zoos’ employees, in general, have a better immune system against animal-induced allergies than other people's. But the answer is quite far from this reasoning. Even I had it in the mind, I didn’t recognize the answer at the first reading.

Any quicker way to recognize the answer?

[RonPurewal]

An interesting CR!

I think the main reasoning is that the zoos’ employees, in general, have a better immune system against animal-induced allergies than other people's.

you can also think of the question in these terms.
this group would be the 'other' 70 percent (to complement the 30 percent mentioned in the passage).

...so, let's go there.
think about WHY this would happen.
if most of the zoo workers have fantastic immune systems, there is only one reasonable real-world explanation.
namely:
• people WITH fantastic immune systems are more likely to work at the zoo (and to KEEP working there).
• people with WORSE immune systems (the 30-percent group) are more likely to AVOID zoo jobs, or to QUIT working there.

there's no other way to explain HOW what you wrote could actually happen.
so, the answer is not 'far from the reasoning' at all... in fact, it's the ONLY possible explanation.

[NL]

Yes, Sifu, that's clear.
Maybe my mind dropped it while searching the answer.

[RonPurewal]

excellent.

(i had to google 'sifu'... i guess that's like 'sensei' in japanese? never seen 'sifu' before. cool.)