Results 1 to 6 of 6

Math Help - unbias estimates and variance?

  1. #1
    Newbie
    Joined
    Apr 2011
    Posts
    17

    unbias estimates and variance?

    consider the unbias estimaters mu1hat = 1/2 xbar + 1/2 ybar. and mu2hates = 1/3 xbar + 2/3 ybar. calculate the variance of mu1hat and mu2hats
    Follow Math Help Forum on Facebook and Google+

  2. #2
    MHF Contributor
    Joined
    May 2010
    Posts
    1,030
    Thanks
    28
    can you work out Var(\bar{x}) = Var \left( \frac{\sum x}{n} \right) ?

    if so, you can use:
    Var(a \bar{x}) = a^2 var(\bar{x})

    which will give you Var(\frac{\bar{x}}{2}) and hence Var(\hat{\mu_1})

    repeat the process to get Var(\hat{\mu_2})


    Finally, you can use:
    Var(C + D) = Var(C) + Var(D) + 2Cov(C,D)

    to get the variance of the sum.
    Follow Math Help Forum on Facebook and Google+

  3. #3
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    I would like to know a lot more information,
    such as the sample sizes, the covariance between the X's and Y's
    the variance of X and also of Y

    AND I guess, both the expected value of the X and Y is this mythical Moo.
    Follow Math Help Forum on Facebook and Google+

  4. #4
    Newbie
    Joined
    Apr 2011
    Posts
    17
    Quote Originally Posted by SpringFan25 View Post
    can you work out Var(\bar{x}) = Var \left( \frac{\sum x}{n} \right) ?

    if so, you can use:
    Var(a \bar{x}) = a^2 var(\bar{x})

    which will give you Var(\frac{\bar{x}}{2}) and hence Var(\hat{\mu_1})

    repeat the process to get Var(\hat{\mu_2})


    Finally, you can use:
    Var(C + D) = Var(C) + Var(D) + 2Cov(C,D)

    to get the variance of the sum.
    Var(a \bar{x}) = a^2 var(\bar{x})
    i have never herd this one it is nt in my sylabus

    covarance is also not in my sylabus and i dont know any resource i cn find to find this one out.. i looked on many website and i not find ...

    also there is not muhat 1 and muhat 2. .. it is muonehat and mutwo hats. like U '',
    Follow Math Help Forum on Facebook and Google+

  5. #5
    Newbie
    Joined
    Apr 2011
    Posts
    17
    Quote Originally Posted by matheagle View Post
    I would like to know a lot more information,
    such as the sample sizes, the covariance between the X's and Y's
    the variance of X and also of Y
    yes so would i

    but is not given

    and yes the expected valuees are mu
    as u obviously were able to figure this without me saying so my omision is justify
    Follow Math Help Forum on Facebook and Google+

  6. #6
    MHF Contributor matheagle's Avatar
    Joined
    Feb 2009
    Posts
    2,763
    Thanks
    5
    Quote Originally Posted by Caption12 View Post
    consider the unbias estimaters mu1hat = 1/2 xbar + 1/2 ybar. and mu2hates = 1/3 xbar + 2/3 ybar. calculate the variance of mu1hat and mu2hats
    and who does moo hates? hates two? moo2hater? moohatter? madhatter?
    I'm confused.
    Follow Math Help Forum on Facebook and Google+

Similar Math Help Forum Discussions

  1. Point Estimates
    Posted in the Advanced Statistics Forum
    Replies: 5
    Last Post: June 21st 2011, 04:08 PM
  2. estimates
    Posted in the Advanced Statistics Forum
    Replies: 2
    Last Post: March 9th 2011, 11:57 PM
  3. Interval estimates?
    Posted in the Statistics Forum
    Replies: 3
    Last Post: May 11th 2010, 10:11 PM
  4. Interval Estimates
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: June 27th 2009, 01:04 AM
  5. Unbiased Estimates
    Posted in the Advanced Statistics Forum
    Replies: 1
    Last Post: November 22nd 2008, 01:15 AM

Search Tags


/mathhelpforum @mathhelpforum