Why Is E Wrong? Pls help

When we're asked to draw a conclusion on CR, we have to think about what MUST be true. We can eliminate any statements that involve assumptions that may or may not be true.

Given:
According to a recent magazine article, of those office employees who typically work 8 hours at the office each day but sometimes say that they will work at home on a particular day, 25 percent actually work less than one hour.
Infer:
Some people (25% of them) spend less time working at home than they typically do in an office. Do we know why? Or how they feel about it? No.

Given:
At the same time, over 90 percent of those same office employees believe they are more productive working at home than working in their office.
Infer:
- 10% of those office employees do not necessarily believe that they are more productive at home. Those 10% might overlap with the 25% who work less than one hour, or they may not.
- Do we know that they are more or less productive? No, we only know what they believe.

a) On average, the office employees working at home for a day work fewer hours than office employees working at the office.
We don't know about ALL employees on average. We only know about the 25%. Maybe the other 75% works more.

b) 10 percent of the office employees are less productive working from home than working in their office.
This is a trap answer. We don't know that they ARE less productive. We know that 90% BELIEVE that they are MORE productive. We don't know if anything about how time spent correlates to productivity.

c) At least 15 percent of the office employees do not define productivity exclusively in terms of the number of hours worked.
If 25% work less than an hour, and 90% believe that they are more productive, then at most there are 10% of people who do NOT believe they are more productive, who also work less than an hour. That means that at least 15% of people overlap into both categories - working less time, but believing they are more productive. If this is true, then it must be the case that these 15% do not define productivity in terms of time spent.

d) At least 25 percent of the office employees can complete the same amount of work in one hour at home as in 8 hours at the office.
We have no information on how much work people actually do. We only have some information on how productive they BELIEVE they are.

e) Some of the office employees make statements regarding their productivity that are not in fact true.
Be careful! Answers about people's thoughts, feelings, or intentions are almost always wrong on CR. Some people work less hours, but believe that they're more productive. Do we know that they're lying? No - it's possible that they do actually accomplish more in one hour at home than 8 hours in the office. Or their beliefs could be wrong, but sincerely held - belief is subjective.

The only answer that MUST be true is C. All of the others may or may not be true, but they involve projecting our own assumptions onto them.

Here's another tip: with CR questions that involve numbers or percents, the right answer will usually address those numbers. Treat it like a quant problem - what do 25% and 90% mean specifically? Would the case be different with different percentages? Sure - if only 50% of people believed that they were more productive, then the 25% and the 50% might not overlap at all, and we couldn't infer anything. With 25% and 90%, they have to overlap.

Here are some other CR questions that involve doing the math:
https://www.beatthegmat.com/property-tax ... tml#716304
https://www.beatthegmat.com/conclusion-t ... tml#582254
https://www.beatthegmat.com/i-m-doubting ... tml#551227
https://www.beatthegmat.com/cr-evaluate- ... tml#558393