What property is an arbitrarily chosen estimator unbiased with respect to?












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$begingroup$


$renewcommand{vector}[1]{vec{#1}}$If I come up with a completely arbitrary estimator, how do I determine what, if anything, it is an unbiased estimator for?



Suppose I have a random finite sample $vector{w}$ of
length $n$ drawn from an arbitrarily chosen distribution $theta$ .



$vector{w}_1$ (the first value in the sample)✱✱ can be thought of
as an estimator of some property.✱



If we're considering $vector{w}_1$ as an estimator
of the variance, it is an extremely bad estimator since it has nothing to do with the variance, even in principle. The variance is an example of a candidate property that could be targeted by $vector{w}_1$, in order to rule it and almost every other property out, I want to insist that my estimator is unbiased.



$vector{w}_1$ is an unbiased estimator of the mean, $bar{theta}$ .
There are better unbiased estimators of the mean, but this is one of them.



How would I go about determining what property of a distribution $left(vector{w}_1-vector{w}_2right)^2$
is an unbiased estimator for? Its definition is "inspired by" the definition of variance, but I don't have
any reason to suspect that the variance is the thing it's actually estimating unbiasedly.



✱ I'm thinking of a property as just a function from
$mathrm{dist}[mathbb{R}] to mathbb{R} cup {bot}$ , like the population mean, population variance,
or population median. It is irrelevant to the notion of a property how a particular family of distributions is
parameterized. I don't know the actual term for this.



✱✱ $vector{w}_1$ is undefined if $vector{w}$ has length zero. Similarly
$(vector{w}_1 - vector{w}_2)^2$ is undefined if $vector{w}$ has length zero or one. As long as a
statistic is defined for all samples above a particular length, it is allowed to be undefined in some places.










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$endgroup$

















    0












    $begingroup$


    $renewcommand{vector}[1]{vec{#1}}$If I come up with a completely arbitrary estimator, how do I determine what, if anything, it is an unbiased estimator for?



    Suppose I have a random finite sample $vector{w}$ of
    length $n$ drawn from an arbitrarily chosen distribution $theta$ .



    $vector{w}_1$ (the first value in the sample)✱✱ can be thought of
    as an estimator of some property.✱



    If we're considering $vector{w}_1$ as an estimator
    of the variance, it is an extremely bad estimator since it has nothing to do with the variance, even in principle. The variance is an example of a candidate property that could be targeted by $vector{w}_1$, in order to rule it and almost every other property out, I want to insist that my estimator is unbiased.



    $vector{w}_1$ is an unbiased estimator of the mean, $bar{theta}$ .
    There are better unbiased estimators of the mean, but this is one of them.



    How would I go about determining what property of a distribution $left(vector{w}_1-vector{w}_2right)^2$
    is an unbiased estimator for? Its definition is "inspired by" the definition of variance, but I don't have
    any reason to suspect that the variance is the thing it's actually estimating unbiasedly.



    ✱ I'm thinking of a property as just a function from
    $mathrm{dist}[mathbb{R}] to mathbb{R} cup {bot}$ , like the population mean, population variance,
    or population median. It is irrelevant to the notion of a property how a particular family of distributions is
    parameterized. I don't know the actual term for this.



    ✱✱ $vector{w}_1$ is undefined if $vector{w}$ has length zero. Similarly
    $(vector{w}_1 - vector{w}_2)^2$ is undefined if $vector{w}$ has length zero or one. As long as a
    statistic is defined for all samples above a particular length, it is allowed to be undefined in some places.










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      $renewcommand{vector}[1]{vec{#1}}$If I come up with a completely arbitrary estimator, how do I determine what, if anything, it is an unbiased estimator for?



      Suppose I have a random finite sample $vector{w}$ of
      length $n$ drawn from an arbitrarily chosen distribution $theta$ .



      $vector{w}_1$ (the first value in the sample)✱✱ can be thought of
      as an estimator of some property.✱



      If we're considering $vector{w}_1$ as an estimator
      of the variance, it is an extremely bad estimator since it has nothing to do with the variance, even in principle. The variance is an example of a candidate property that could be targeted by $vector{w}_1$, in order to rule it and almost every other property out, I want to insist that my estimator is unbiased.



      $vector{w}_1$ is an unbiased estimator of the mean, $bar{theta}$ .
      There are better unbiased estimators of the mean, but this is one of them.



      How would I go about determining what property of a distribution $left(vector{w}_1-vector{w}_2right)^2$
      is an unbiased estimator for? Its definition is "inspired by" the definition of variance, but I don't have
      any reason to suspect that the variance is the thing it's actually estimating unbiasedly.



      ✱ I'm thinking of a property as just a function from
      $mathrm{dist}[mathbb{R}] to mathbb{R} cup {bot}$ , like the population mean, population variance,
      or population median. It is irrelevant to the notion of a property how a particular family of distributions is
      parameterized. I don't know the actual term for this.



      ✱✱ $vector{w}_1$ is undefined if $vector{w}$ has length zero. Similarly
      $(vector{w}_1 - vector{w}_2)^2$ is undefined if $vector{w}$ has length zero or one. As long as a
      statistic is defined for all samples above a particular length, it is allowed to be undefined in some places.










      share|cite|improve this question









      $endgroup$




      $renewcommand{vector}[1]{vec{#1}}$If I come up with a completely arbitrary estimator, how do I determine what, if anything, it is an unbiased estimator for?



      Suppose I have a random finite sample $vector{w}$ of
      length $n$ drawn from an arbitrarily chosen distribution $theta$ .



      $vector{w}_1$ (the first value in the sample)✱✱ can be thought of
      as an estimator of some property.✱



      If we're considering $vector{w}_1$ as an estimator
      of the variance, it is an extremely bad estimator since it has nothing to do with the variance, even in principle. The variance is an example of a candidate property that could be targeted by $vector{w}_1$, in order to rule it and almost every other property out, I want to insist that my estimator is unbiased.



      $vector{w}_1$ is an unbiased estimator of the mean, $bar{theta}$ .
      There are better unbiased estimators of the mean, but this is one of them.



      How would I go about determining what property of a distribution $left(vector{w}_1-vector{w}_2right)^2$
      is an unbiased estimator for? Its definition is "inspired by" the definition of variance, but I don't have
      any reason to suspect that the variance is the thing it's actually estimating unbiasedly.



      ✱ I'm thinking of a property as just a function from
      $mathrm{dist}[mathbb{R}] to mathbb{R} cup {bot}$ , like the population mean, population variance,
      or population median. It is irrelevant to the notion of a property how a particular family of distributions is
      parameterized. I don't know the actual term for this.



      ✱✱ $vector{w}_1$ is undefined if $vector{w}$ has length zero. Similarly
      $(vector{w}_1 - vector{w}_2)^2$ is undefined if $vector{w}$ has length zero or one. As long as a
      statistic is defined for all samples above a particular length, it is allowed to be undefined in some places.







      statistics






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      asked Dec 24 '18 at 18:30









      Gregory NisbetGregory Nisbet

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