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# What is the median number of employees assigned per project

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Re: What is the median number of employees assigned per project  [#permalink]

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01 Sep 2017, 15:00
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ITIZCODE wrote:
What is the median number of employees assigned per project for the projects at Company Z?

(1) 25 percent of the projects at Company Z have 4 or more employees assigned to each project.
(2) 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project

Target question: What is the median number of employees assigned per project?

Statement 1: 25 percent of the projects at Company Z have 4 or more employees assigned to each project.
Let's pretend that there are 4 projects altogether.
There are several sets of values that meet this condition. Here are two:
Case a: the set of numbers representing employees per project are {1, 1, 1, 4} in which case the median is 1
Case b: the set of numbers representing employees per project are {2, 2, 2, 4} in which case the median is 2
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project.
Using logic similar to the above, we can show that statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined:
35% projects have 2 employees OR FEWER, and 25% of the projects have 4 employees OR MORE. So, 40% projects have EXACTLY 3 employees.

To find the median, we must find the middlemost value when all of the values are listed in ASCENDING order.
So, the first 35% of the numbers will be 1's and 2's.
Then next 40% of the numbers will be 3's
And the last 25% of the numbers will be 4, 5's, etc

As you can see, the MIDDLEMOST value will be 3. In other words, the median must be 3.
Since we can answer the target question with certainty, the combined statements are SUFFICIENT

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Re: What is the median number of employees assigned per project  [#permalink]

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24 Nov 2017, 09:07
Okay, I know this question has been asked before, but people's answers to it aren't helping me, so if anyone can re-phrase then that would be hugely appreciated.

I do not understand how the statements do not allow there to be projects that have 5, 10, 15, 20, 1000 etc people working on them. Let's say that there are 100 projects at Company Z.

(1) 25 projects have 4 or more employees.
This could be laid out like this:
Project number 75 has 4 employees.
Project number 76 has 5 employees.
Project number 77 has 6 employees.
...
Project number 100 - 29 employees.

Then once we know that there are projects with 0, 1, 2, and 3 employees (and this information is gleaned from statement (2) as discussed earlier in the thread), we have a collection of 100 projects, with 1, 2, 2, 2, 2 (x 35 projects), 3 (x 40 projects), 4, 5, 6, 7 ... 29 employees. In this case the median has to be 15, not 3.

Does my analysis make sense?
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Re: What is the median number of employees assigned per project  [#permalink]

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17 Jan 2018, 15:17
priyamne wrote:
ITIZCODE wrote:
What is the median number of employees assigned per project for the projects at Company Z?

(1) 25 percent of the projects at Company Z have 4 or more employees assigned to each project.
(2) 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project

Ans: : Median is the middle value. Statements 1 and 2 alone give us insufficient data but when we combine both of them we see that 25 % have 4 or more and 35% have 2 or less therefore 40 %have 3 employees. Therefore the median would be 3 and the answer is (C).

I understand that we're looking for the median and that each statement alone only tell us PART of what we want to know...further, I understand adding up both %s [25 & 35] and deducing that 40% have 3 employees.
- HOWEVER, how do we know that 40% contains the median? What if we changed the numbers in Statement 1 & 2 both to 35? In this case, 30% would be left for 3 employees...how would this affect the answer?
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Re: What is the median number of employees assigned per project  [#permalink]

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18 Jan 2018, 08:16
LakerFan24 wrote:
priyamne wrote:
ITIZCODE wrote:
What is the median number of employees assigned per project for the projects at Company Z?

(1) 25 percent of the projects at Company Z have 4 or more employees assigned to each project.
(2) 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project

Ans: : Median is the middle value. Statements 1 and 2 alone give us insufficient data but when we combine both of them we see that 25 % have 4 or more and 35% have 2 or less therefore 40 %have 3 employees. Therefore the median would be 3 and the answer is (C).

I understand that we're looking for the median and that each statement alone only tell us PART of what we want to know...further, I understand adding up both %s [25 & 35] and deducing that 40% have 3 employees.
- HOWEVER, how do we know that 40% contains the median? What if we changed the numbers in Statement 1 & 2 both to 35? In this case, 30% would be left for 3 employees...how would this affect the answer?

It won't change the answer. Say there are 20 projects.
If 35% have 4 or more employees, it means 7 projects have 4 or more employees.
If 35% have 2 or fewer employees, it means 7 projects have 2 or fewer employees.
The leftover 30% i.e. 6 projects have 3 employees.

To find the median, you will need to arrange the number of employees in increasing order

1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 5, 6, 6, 7

The one in the middle will be 3.
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What is the median number of employees assigned per project  [#permalink]

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15 Aug 2018, 21:29
Bunuel wrote:
ITIZCODE wrote:
What is the median number of employees assigned per project for the projects at Company Z?

(1) 25 percent of the projects at Company Z have 4 or more employees assigned to each project.
(2) 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project

What is the median number of employees assigned per project for the projects at Company Z?

(1) 25 percent of the projects at Company Z have 4 or more employees assigned to each project. Not sufficient on its own.

(2) 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project. Not sufficient on its own.

(1)+(2) Since 35% of of the projects have 2 or fewer ($$\leq{2}$$)employees and 25% of the projects have 4 or more ($$\geq{4}$$) employees, then 100%-(25%+35%)=40% of the projects have exactly 3 employees assigned to each of them. So, the median number of employees assigned per project is 3. Sufficient.

To elaborate more: consider there are 100 projects: $$\{p_1, \ p_2, \ ... , \ p_{100}\}$$. The values of $$p_1$$ to $$p_{35}$$ will be 0, 1, or 2; the values of $$p_{36}$$ to $$p_{75}$$ will be exactly 3; the values of $$p_{76}$$ to $$p_{100}$$ will be 4 or more. $$Median=\frac{p_{50}+p_{51}}{2}=\frac{3+3}{2}=3$$.

For example list can be: $$\{2, \ 2, \ 2, \ ..., \ (p_{35}=2), \ (p_{36}=3), \ 3, \ ..., \ (p_{75}=3), \ (p_{76}=4), \ 4, \ ..., \ (p_{100}=4)\}$$;
OR:
$$\{0, \ 0, \ 1, \ 1, \ 1, \ 2, \ 2, \ ..., \ (p_{35}=2), \ (p_{36}=3), \ 3, \ ..., \ (p_{75}=3), \ (p_{76}=4), \ 5, \ 7, \ 27, \ ..., \ (p_{100}=10000)\}$$ (of course there are a lot of other breakdowns).

In any case median=3.

Hope it's clear.

P.S. Please post PS questions in the PS subforum: http://gmatclub.com/forum/gmat-problem-solving-ps-140/ and DS questions in the DS subforum: http://gmatclub.com/forum/gmat-data-sufficiency-ds-141/ No posting of PS/DS questions is allowed in the main Math forum.

this is how I thought about it...

first 35 projects have 2 or fewer assigned to each so that can be 0,1 or 2

next 25 that is from 36 - 61 have 4 or more....so that can be anything from 4,5,6...

so the last 39 ie from 62- 100 must be more than 4?

so the median can be either 4 or above 4

please correct my line of thinking I'm lost...
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Re: What is the median number of employees assigned per project  [#permalink]

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26 Aug 2018, 04:18
ITIZCODE wrote:
What is the median number of employees assigned per project for the projects at Company Z?

(1) 25 percent of the projects at Company Z have 4 or more employees assigned to each project.
(2) 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project

Statement One: # of employees per project 4 or more --- > 4 or 5

Statement Two: # of employees per project 2 or less ----- > 2 or 1

Combining both statements: 1+2+4+5 ---> median $$\frac{2+4}{2}$$= $$3$$

hence C

can anyone comment if my reasoning/approach is correct ?
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What is the median number of employees assigned per project  [#permalink]

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29 Nov 2018, 03:41
roygush wrote:
What is the median number of employees assigned per project for the projects at Company Z?

(1) 25 percent of the projects at Company Z have 4 or more employees assigned to each project.
(2) 35 percent of the projects at Company Z have 2 or fewer employees assigned to each project

Ruled out quickly A,B,D.
remained with C, E.
chose E.
then looked here:
http://gmatclub.com/forum/what-is-the-m ... 31892.html

and i still dont understand bunuel's way.
why the employees who are not in the 25% or 35% must have exactly 3 employees?
thanks

Answer is C (why? explained below)

25% project have 4 OR more(5,6,7,...) employees ; No picture of remaining 75% slab ;
35% project have 2 OR less(0,1) employees ; No clue about remaining 65% slab ;

Taking both stems (1) & (2),

25% project have 4 OR more(5,6,7,...) employees & 35% project have 2 OR less(0,1) employees ;
Now, remaining 40% [100%-(25%+35%)] must have exactly 3 employees ; Since, If it had say 4 OR more(5,6,7,...) employees then it should have been included in 25% slab (the question clearly specifies that only 25% slab has 4 OR more) ; Similarly, If it had 2 OR less(0,1) employees than it should have been under 35% slab (according to the question). So, 40% slab must and must have employees=3 (and Hence, the median value) ; And One may ask why median is 3? Here we kept 40% slab between 25% & 35% ? Here we arrange the set of data in an order as per their values(say, ascending)- 35%(0,1,2,.... OR 0,0,2,... OR 1,1,2,...OR 2,2,2,.... it would be 1st-35th term=total 35 terms) 40%(3,3,3,3,.... it would be 36th-75th term=total 40 terms) 25%(4,5,6,7,... OR 4,5,5,6,... OR 4,4,4,.... OR 4,4,6,..99,100,..,1000,1001,... it would be 76th-100th term OR last 25 terms) ; Median in this case lies in 40% slab (since 100 is the total here and even no. so median will be sum of 50th & 51th term which lies in 40% slab) ;
Hope it clears your doubt ;

(P.S. I had the same doubt but gave a look at the question once again after I saw ur comment; In a way it helped me ; Thnx fella !! CHEERS !!
What is the median number of employees assigned per project   [#permalink] 29 Nov 2018, 03:41

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