Hey there! Sign in to join this conversationNew here? Join for free

[OCR not MEI] Statistics 2: Deciding on when to used an unbiased estimator Watch

    • Thread Starter

    I have found throughout S2 that I have confusion with when and when not to use the unbiased estimator for the variance.

    I understand if you have a sample from a population of UNKNOWN variance, you must use it then. However, there seems to be discontinuity in some questions. Sometimes I have noticed that with this question: (taken from June 2012 S2 q2 i):

    For the continuous random variable V, it is known that E(V) = 72.0. The mean of a random sample of 40 observations of V is denoted V bar. Given that P(V bar < 71.2) = 0.35, estimate the value of Var(V).

    Now I managed to get Var(V) before applying the unbiased estimator. I then applied the unbiased estimating method (multiplying by the sample size/ sample size -1) and that was not the answer.

    However, when you are given data for the sample of a population (given the summation information) you have to use the unbiased estimator.

    I am not entirely sure why, but can someone please explain this to me.

    Thank you,

    •  Official Rep

     Official Rep
    Sorry you've not had any responses about this. Are you sure you've posted in the right place? Here's a link to our subject forum which should help get you more responses if you post there.

    You can also find the Exam Thread list for A-levels here and GCSE here. :dumbells:

    Just quoting in Puddles the Monkey so she can move the thread if needed
    (Original post by Puddles the Monkey)
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    What's your favourite Christmas sweets?
    Useful resources

    Make your revision easier


    Maths Forum posting guidelines

    Not sure where to post? Read the updated guidelines here


    How to use LaTex

    Writing equations the easy way

    Student revising

    Study habits of A* students

    Top tips from students who have already aced their exams

    Study Planner

    Create your own Study Planner

    Never miss a deadline again

    Polling station sign

    Thinking about a maths degree?

    Chat with other maths applicants

    Can you help? Study help unanswered threads

    Groups associated with this forum:

    View associated groups
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.