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Register now and save up to $200 Available with Beat the GMAT members only code • 5-Day Free Trial 5-day free, full-access trial TTP Quant Available with Beat the GMAT members only code • Magoosh Study with Magoosh GMAT prep Available with Beat the GMAT members only code • Free Practice Test & Review How would you score if you took the GMAT Available with Beat the GMAT members only code ## Need better explanation: Statistics OG13 Question# 139 tagged by: Brent@GMATPrepNow This topic has 3 expert replies and 3 member replies tanvis1120 Senior | Next Rank: 100 Posts Joined 28 Dec 2013 Posted: 95 messages Followed by: 4 members Thanked: 2 times Target GMAT Score: 750 #### Need better explanation: Statistics OG13 Question# 139 Wed Jul 23, 2014 3:25 pm Elapsed Time: 00:00 • Lap #[LAPCOUNT] ([LAPTIME]) Q. 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. My answer is E. Explanation: Let the total number of projects be 100. St 1: 25% or 25 projects have 4 or more employees. Here, we have no idea about the highest threshold of employees (>4 can 5 or 20 etc.). Also, what about the remaining 75 project? So, the median cannot be calculated. (Not Sufficient) St 2: 35% or 35 projects have 2 or fewer employees. We cannot determine the median from this. 35 projects can have different number of employees,2 or 1. What about the remaining 65? (Not Sufficient) St1 + St2: 100-(25+35) = 40 projects. We have no idea about the number of employees that each of the remaining project has. (Not Sufficient) OG13 says that the correct answer is C (Calculated median is 3). But I am having hard time understanding their explanation. If your answer is C too, please explain it to me clearly. Thank You in Advance ! Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums! ### GMAT/MBA Expert Brent@GMATPrepNow GMAT Instructor Joined 08 Dec 2008 Posted: 10758 messages Followed by: 1212 members Thanked: 5140 times GMAT Score: 770 Wed Jul 23, 2014 3:28 pm tanvis1120 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. 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 Answer = C Cheers, Brent _________________ Brent Hanneson – Founder of GMATPrepNow.com Use our video course along with Check out the online reviews of our course GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months! ### GMAT/MBA Expert Brent@GMATPrepNow GMAT Instructor Joined 08 Dec 2008 Posted: 10758 messages Followed by: 1212 members Thanked: 5140 times GMAT Score: 770 Wed Jul 23, 2014 3:36 pm tanvis1120 wrote: Q. 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. My answer is E. Explanation: Let the total number of projects be 100. St 1: 25% or 25 projects have 4 or more employees. Here, we have no idea about the highest threshold of employees (>4 can 5 or 20 etc.). Also, what about the remaining 75 project? So, the median cannot be calculated. (Not Sufficient) St 2: 35% or 35 projects have 2 or fewer employees. We cannot determine the median from this. 35 projects can have different number of employees,2 or 1. What about the remaining 65? (Not Sufficient) St1 + St2: 100-(25+35) = 40 projects. We have no idea about the number of employees that each of the remaining project has. (Not Sufficient) OG13 says that the correct answer is C (Calculated median is 3). But I am having hard time understanding their explanation. If your answer is C too, please explain it to me clearly. Thank You in Advance ! I've highlighted the problem above. Statement 1 accounts for projects with 4 or more employees Statement 2 accounts for projects with 2 or fewer employees The remaining 40% of projects must have 3 employees Cheers, Brent _________________ Brent Hanneson – Founder of GMATPrepNow.com Use our video course along with Check out the online reviews of our course GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months! tanvis1120 Senior | Next Rank: 100 Posts Joined 28 Dec 2013 Posted: 95 messages Followed by: 4 members Thanked: 2 times Target GMAT Score: 750 Wed Jul 23, 2014 3:44 pm Ohhh... I got the target question totally wrong!!! I got it now.. I was thinking in an entirely different path, something weird !!! Thanks ! ### GMAT/MBA Expert Brent@GMATPrepNow GMAT Instructor Joined 08 Dec 2008 Posted: 10758 messages Followed by: 1212 members Thanked: 5140 times GMAT Score: 770 Wed Jul 23, 2014 4:26 pm tanvis1120 wrote: Ohhh... I got the target question totally wrong!!! I got it now.. I was thinking in an entirely different path, something weird !!! Thanks ! If you read the target question as asking for the mean (and not the median), then the correct answer would, indeed, be E Cheers, Brent _________________ Brent Hanneson – Founder of GMATPrepNow.com Use our video course along with Check out the online reviews of our course GMAT Prep Now's comprehensive video course can be used in conjunction with Beat The GMAT’s FREE 60-Day Study Guide and reach your target score in 2 months! ### Top Member GMATinsight Legendary Member Joined 10 May 2014 Posted: 998 messages Followed by: 21 members Thanked: 203 times Thu Jul 24, 2014 12:48 am tanvis1120 wrote: Q. 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. CONCEPT : Median is the middle term of the set when terms are arranged in ascending/descending order. If the number of terms is even in the set then the average of two middle terms of the set is called median Let, there are 100 projects in the set which according to Descending order of assigned number of employees is represented as {1, 2, 3, .....34, 35, 36, 37.......98, 99, 100} Since the number of terms in the set is even therefore the Median number of Employees assigned will be the Average of No of employees assigned to 50th and 51st Project Statement 1) 25% of the projects at company Z have 4 or more employees assigned to each project. {1, 2, 3, .....24, 25, 26, 27.......98, 99, 100} i.e. Red Projects are representing the number of employees 4 or more in descending order The number of employees assigned to 50th ans 51st project are unknown therefore, INSUFFICIENT Statement 2)35% of the projects at company Z have 2 or fewer employees assigned to each project. {1, 2, 3, .....24, 25,...... 66, 67.......98, 99, 100} i.e. Blue Projects are representing the number of employees 4 or more in descending order The number of employees assigned to 50th ans 51st project are unknown therefore, INSUFFICIENT Combining the two statements {1, 2, 3, .....24, 25,26, 27......64, 65, 66, 67.......98, 99, 100} Since Red are representing equal to or Greater than 4 employees and Blue are representing lesser than or equal to 2 employees projects then remaining projects must have employees between 2 and 4 i.e. number of employees for Black projects = 3 i.e. 50th and 51st project have 3 emloyees each. i.e. Median Number of employees - 3 Answer: Option C _________________ Prosper!!! 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tanvis1120 Senior | Next Rank: 100 Posts
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Thu Jul 24, 2014 11:10 am
Thanks.. Nice explanation!

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