As per your request, I thought I'd take this one on in long form, realistic fashion (outlining the passage itself, and describing the effect of each answer choice). Let's take a look:
A confidential survey revealed that 75 percent of the employees of Company P are dissatisfied with their jobs. However, an investigation into working conditions at the company showed nothing uncommonly bad. Therefore, Company P's consulting firm concluded that the employees' dissatisfaction must result from an unusually high incidence of psychological problems on their part.
Conclusion: Dissatisfaction result of employee psych problems
Premises: 75% of employees dissatisfied, nothing uncommonly bad
Assumptions: [There are many here, which we would expect, given that there are 4 answer choices that take advantage of these assumptions; I'll try to hit some up without looking at the answer choices] 75% is an above average amount of dissatisfaction. Psychological problems connect to job dissatisfaction. Something other than working conditions is affecting things.
That's all I can think of off the top of my head. It's not necessarily important to write these out, but I like going into EXCEPT questions with at least a little bit of ammo, as I'm going to have to find four answer choices that weaken.
Each of the following, if true, casts doubt on the consulting firm's conclusion EXCEPT:
A In the investigation of working conditions, no account was taken of the fact that for the past year many Company P employees worked on a joint venture with Company O, at Company O's facilities.
PROBLEM: Definitely weakens. This would relate most closely to the third assumption I guessed at. Working conditions at P aren't the issue, but at O.
B. Workers in many companies are dissatisfied although there are no apparent problems with their working conditions.
PROBLEM: Ha! I saw this one coming with my first assumption. Definitely weakens, because now there's no way to conclude they have psych problems, because they're the same as everyone else.
C. The consulting firm's conception of what constitutes uncommonly bad working conditions is not identical to that of Company P's employees.
PROBLEM: Didn't see this one coming, but it definitely weakens. If the consulting firm thinks the working conditions are fine, but the employees don't, it could still be the working conditions making the employees unhappy.
D. The reasons given by Company P's employees for their dissatisfaction varied greatly from employee to employee.
PROBLEM: This doesn't weaken much (what people claim to be true is always dangerous on the GMAT), but it's enough. After all, if everyone has different reasons, it would be silly to conclude that everyone's reason is actually the same (psych problems).
E. A battery of tests performed on Acme's employees one month ago revealed no significant psychological stresses or problems
ANSWER: This doesn't weaken at all. We don't know anything about Acme, including how dissatisfied people are. Maybe at ACME, there is a really low dissatisfaction rate, in which case this would STRENGTHEN the argument. Because there's no way to know, this doesn't weaken.
Hope that helps!
Tommy Wallach | Manhattan GMAT Instructor | San Francisco
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