OG 13- DS- Q139

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OG 13- DS- Q139

by Suz » Fri Aug 03, 2012 7:47 pm
What is the median number of employees assigned per project for the projects at company Z?

1)25% of the projects at Company Z have 4 or more employees assigned to each project

2)35% of the projects at Company Z have 2 or fewer employees assigned to each project


--I'm a little confused with the explanation in the OG. Esp the bit about C being the correct answer.Any inputs will be appreciated!



Thanks
Source: — Data Sufficiency |

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by eagleeye » Fri Aug 03, 2012 8:05 pm
Suz wrote:What is the median number of employees assigned per project for the projects at company Z?

-I'm a little confused with the explanation in the OG. Esp the bit about C being the correct answer.Any inputs will be appreciated!

Thanks
We need to see if we can determine the median. First of all the employee numbers will be integers. With that out of the way, let's look at the options:

1)25% of the projects at Company Z have 4 or more employees assigned to each project
This tells us that 25% of projects have 4,5,6,7,8,9.... or more employees assigned to the project. This means that for the other 75%, there are either 3, 2, 1, or 0. We don't know how many of that 75% have 3 assigned to them or 2 etc. Insufficient.


2)35% of the projects at Company Z have 2 or fewer employees assigned to each project
Now we are told that 35% of projects have 0,1 or 2 employees assigned to the project. The other 65% can have 3,4,5,6,7,8....or more people assigned to it in any distribution. Insufficient.

Together:

We know that 25% have 4,5,6..... people.
We also know that 35% have 0,1, or 2 people.

Now on the number line we have 0,1,2,THREE,4,5,6,7,8,.... as the possible integer number of employees.
We know that for the first 35% of distribution we have 0,1 or 2 people.
We also know that for the last 25% of the distribution we have 4,5,6,7,8,9...people.

This means that for the remaining 40% of the projects, we MUST have exactly 3 employees.
So, finally we have something like this
[0%]-----0,1,2------[35%]------3-------[75%]-----4,5,6,7,8,...-----[100%]. Clearly the value right in the middle of the distribution (50%) is 3. Hence C is sufficient.

Let me know if this helps :)

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by Suz » Fri Aug 03, 2012 8:14 pm
That does help actually. I guess I should have visualized it like that. so we're basically looking at where the 50% mark lies-and in this ascending order, since it has to be an integer- it can only be 3.

Thanks so much!

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by Anurag@Gurome » Fri Aug 03, 2012 8:26 pm
Suz wrote:What is the median number of employees assigned per project for the projects at company Z?

1)25% of the projects at Company Z have 4 or more employees assigned to each project

2)35% of the projects at Company Z have 2 or fewer employees assigned to each project


--I'm a little confused with the explanation in the OG. Esp the bit about C being the correct answer.Any inputs will be appreciated!



Thanks
(1) Median is the value that separates the upper and lower half of the sample. (1) gives that 25% of projects have 4 or more employees to each project . But the % of projects that have less than 4 employees is not given. So, (1) is NOT SUFFICIENT.

(2) From this statement, the % of projects that have more than 2 employees is not given. As above, (2) is also NOT SUFFICIENT.

Combining (1) and (2), 35% projects have 2 or fewer employees, 25% of the projects have 4 or more employees, so the remaining % of projects = 100 - (35 + 25) = 40% projects should have exactly 3 employees (between 2 and 4).
Therefore, median number of employees assigned per project = 3

The correct answer is [spoiler](C)[/spoiler].
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
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