Welcome! Check out our free B-School Guides to learn how you compare with other applicants.
Login or Register
 

candidate selection -- probability

This topic has 1 expert reply and 3 member replies
pappueshwar Really wants to Beat The GMAT! Default Avatar
Joined
01 Oct 2010
Posted:
234 messages
Followed by:
4 members
Thanked:
5 times
Target GMAT Score:
680
candidate selection -- probability Post Sat Feb 04, 2012 10:50 pm
Elapsed Time: 00:00
  • Lap #[LAPCOUNT] ([LAPTIME])
    hi all,
    can any one explain how stmnt 2 is also a good choice.

    the answer is: D

    64 candidates are competing for 5 positions at a consulting firm. The hiring process consists of 3 interviews. After each interview, n% of the remaining candidates will be dismissed. The candidates will be selected from among those complete all three rounds. Each candidate is equally qualified and has an equal probability of getting hired at every point in the process. What is the probability that a candidate will complete all three interviews but fail to get the job?

    (1) n = 25

    (2) 12 candidates completed the first interview but were dismissed after the second interview.

    Need free GMAT or MBA advice from an expert? Register for Beat The GMAT now and post your question in these forums!
    WhiteWNNoise Just gettin' started! Default Avatar
    Joined
    04 Feb 2012
    Posted:
    7 messages
    Thanked:
    1 times
    Post Sun Feb 05, 2012 12:44 pm

    sanju09 GMAT Instructor
    Joined
    21 Jan 2009
    Posted:
    3262 messages
    Followed by:
    48 members
    Thanked:
    190 times
    GMAT Score:
    760
    Post Tue Feb 07, 2012 3:04 am
    pappueshwar wrote:
    hi all,
    can any one explain how stmnt 2 is also a good choice.

    the answer is: D

    64 candidates are competing for 5 positions at a consulting firm. The hiring process consists of 3 interviews. After each interview, n% of the remaining candidates will be dismissed. The candidates will be selected from among those complete all three rounds. Each candidate is equally qualified and has an equal probability of getting hired at every point in the process. What is the probability that a candidate will complete all three interviews but fail to get the job?

    (1) n = 25

    (2) 12 candidates completed the first interview but were dismissed after the second interview.
    If 12 candidates completed the first interview but were dismissed after the second interview, then 12 is equal to n percent the remaining candidates exposed to the interview number 2. It’s sort of an exponential decay where the number of remaining candidates exposed to the interview number 2 can be had from the expression 64 X [1 - (n/100) ^1].

    Hence, n percent of 64 X [1 - (n/100) ^1] is 12. Solve and neglect the impossible (75) possibility and believe n = 25, then call statement (2) sufficient if you understand why statement (1) is sufficient.

    _________________
    The laws of nature are but the mathematical thoughts of God. ~Euclid

    GMAT/MBA Expert

    tpr-becky GMAT Instructor
    Joined
    21 Apr 2010
    Posted:
    509 messages
    Followed by:
    69 members
    Thanked:
    175 times
    GMAT Score:
    750
    Post Tue Feb 07, 2012 1:29 pm
    The trick of this problem is recognizing that you need to do two things - percent and then probability. The probability part will be easy if you know the percent because you can figure out how many candidates are left and the probability of not being the one picked.

    Statement 1 tells you the percent - in theory you could subract 25% of 64, then 25% of the result then 25% of that result and then you would how many total people are left and can calculate the possibility of one of them not being picked. So it is sufficient (you would never want to do all that work on the actual GMAT).

    Statement 2 says that 12 candidates = n% of the number of candidates after the first cut. since the percentage remains stable you could find out what percent that is - [(65(1-n/100))1-n/100] = 12 This is ultimately solveable so it is sufficient - therefore the Answer s D.

    _________________
    Becky
    Master GMAT Instructor
    The Princeton Review
    Irvine, CA

    Free GMAT Practice Test How can you improve your test score if you don't know your baseline score? Take a free online practice exam. Get started on achieving your dream score today! Sign up now.
    amit.trivedi@ymail.com GMAT Destroyer!
    Joined
    09 Nov 2010
    Posted:
    934 messages
    Followed by:
    14 members
    Thanked:
    59 times
    Test Date:
    N.A
    Target GMAT Score:
    750
    Post Sun Mar 18, 2012 11:08 pm
    In statemen 2: All I am getting is n = 75 or n = 25.

    As per normal DS rules, the statement 2 is insufficient.

    But in this question, go back and solve the entire process as mentioned in the stimulus.

    With n = 75%, in the end there is only one candidate left after the clearing of all the 3 interviews. There are 5 positions and only one candidate selected from a lot of 64 candidates.

    The stimulus very clearly states that 'The candidates will be selected from among those complete all three rounds'.

    So n = 75 becomes wrong...

    Now put in 25 and you will see that it satisfies the conditions...

    A bit tricky in the end, but got to find a solution for that as well...


    Hope this helped...

    _________________
    IT IS TIME TO BEAT THE GMAT

    LEARNING, APPLICATION AND TIMING IS THE FACT OF GMAT AND LIFE AS WELL... KEEP PLAYING!!!

    Whenever you feel that my post really helped you to learn something new, please press on the 'THANK' button.

    Best Conversation Starters

    1 varun289 42 topics
    2 guerrero 21 topics
    3 sana.noor 20 topics
    4 killerdrummer 18 topics
    5 sanaa.rizwan 14 topics
    See More Top Beat The GMAT Members...

    Most Active Experts

    1 image description Brent@GMATPrepNow

    GMAT Prep Now Teacher

    202 posts
    2 image description GMATGuruNY

    The Princeton Review Teacher

    140 posts
    3 image description Anju@Gurome

    Gurome

    113 posts
    4 image description Jim@StratusPrep

    Stratus Prep

    92 posts
    5 image description Jon@Admissionado

    Admissionado

    45 posts
    See More Top Beat The GMAT Experts