Standard Deviation Around an Arbitrary MeanMotivation behind standard deviation?Variance and Standard Deviation of multiple dice rollsRelationships between mean and standard deviation when one variable is linear function of anotherStandard deviation with exponential distributionstandard deviation probability of a poission distributionStandard deviation and probability in a problemStandard Deviation Divided by Errorintepretation of standard deviation for geometric mean$n$ vs $n-1$ for the standard deviationCalculating the standard deviation of a distribution around a varying mean

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Standard Deviation Around an Arbitrary Mean


Motivation behind standard deviation?Variance and Standard Deviation of multiple dice rollsRelationships between mean and standard deviation when one variable is linear function of anotherStandard deviation with exponential distributionstandard deviation probability of a poission distributionStandard deviation and probability in a problemStandard Deviation Divided by Errorintepretation of standard deviation for geometric mean$n$ vs $n-1$ for the standard deviationCalculating the standard deviation of a distribution around a varying mean













1












$begingroup$


I'm collecting data from x and y axis offset from origin of the impact points of rounds I've shot at a target, and I've calculated my standard deviations in the x and y directions as $ sigma_x $ and $ sigma_y $ respectively from their variances, and I have also calculated the standard deviation of the root of the sums of their squares (the magnitude of the distance from the origin/bull's eye) as $sigma_r$. Now I know that these values are deviations around the mean value of each variable, which characterizes my shot grouping. I'm seeking to find my standard deviation away from the origin as well, i.e. I'm wanting to know how far I'm deviating away from the center of the target versus how far I'm deviating from the calculated center of my grouping. Would this value just be the calculation of the $sigma^2$ and $sigma$ around a mean of 0 in all the variables so that I have a measure of deviation from perfect, or is this the incorrect way to go about the problem. All standard deviations used are population standard deviations, e.g. $$ sigma^2 = sum_i=1^n left ( frac1n(x_i - mu)^2 right ) ;; ; ; ; sigma = sqrtsigma^2 $$ where in the case in question, $mu$ would be taken to be 0, leaving just the sums of the squares as the variance.










share|cite|improve this question









$endgroup$











  • $begingroup$
    You seem to be interested in the two second moments about the origin, an important notion, though closely related to variance.
    $endgroup$
    – André Nicolas
    Nov 9 '14 at 6:17










  • $begingroup$
    I believe what I'm asking is if I have the correct idea for the calculation of the second moment about the origin.
    $endgroup$
    – Doryan Miller
    Nov 9 '14 at 6:24










  • $begingroup$
    Yes, it is right.
    $endgroup$
    – André Nicolas
    Nov 9 '14 at 6:26










  • $begingroup$
    Note the formula $E(X^2) = Var(X) + mu^2$, so you don't need to do a whole new calculation if you already know $mu$ and $sigma_x$.
    $endgroup$
    – user187373
    Nov 9 '14 at 7:49










  • $begingroup$
    If I'm reading that correctly, what I'm really just searching for, going by the name of the second moment around the origin, is merely the expected value of the square of my data, which is the first raw moment around the mean plus the square of said mean?
    $endgroup$
    – Doryan Miller
    Nov 9 '14 at 15:17















1












$begingroup$


I'm collecting data from x and y axis offset from origin of the impact points of rounds I've shot at a target, and I've calculated my standard deviations in the x and y directions as $ sigma_x $ and $ sigma_y $ respectively from their variances, and I have also calculated the standard deviation of the root of the sums of their squares (the magnitude of the distance from the origin/bull's eye) as $sigma_r$. Now I know that these values are deviations around the mean value of each variable, which characterizes my shot grouping. I'm seeking to find my standard deviation away from the origin as well, i.e. I'm wanting to know how far I'm deviating away from the center of the target versus how far I'm deviating from the calculated center of my grouping. Would this value just be the calculation of the $sigma^2$ and $sigma$ around a mean of 0 in all the variables so that I have a measure of deviation from perfect, or is this the incorrect way to go about the problem. All standard deviations used are population standard deviations, e.g. $$ sigma^2 = sum_i=1^n left ( frac1n(x_i - mu)^2 right ) ;; ; ; ; sigma = sqrtsigma^2 $$ where in the case in question, $mu$ would be taken to be 0, leaving just the sums of the squares as the variance.










share|cite|improve this question









$endgroup$











  • $begingroup$
    You seem to be interested in the two second moments about the origin, an important notion, though closely related to variance.
    $endgroup$
    – André Nicolas
    Nov 9 '14 at 6:17










  • $begingroup$
    I believe what I'm asking is if I have the correct idea for the calculation of the second moment about the origin.
    $endgroup$
    – Doryan Miller
    Nov 9 '14 at 6:24










  • $begingroup$
    Yes, it is right.
    $endgroup$
    – André Nicolas
    Nov 9 '14 at 6:26










  • $begingroup$
    Note the formula $E(X^2) = Var(X) + mu^2$, so you don't need to do a whole new calculation if you already know $mu$ and $sigma_x$.
    $endgroup$
    – user187373
    Nov 9 '14 at 7:49










  • $begingroup$
    If I'm reading that correctly, what I'm really just searching for, going by the name of the second moment around the origin, is merely the expected value of the square of my data, which is the first raw moment around the mean plus the square of said mean?
    $endgroup$
    – Doryan Miller
    Nov 9 '14 at 15:17













1












1








1





$begingroup$


I'm collecting data from x and y axis offset from origin of the impact points of rounds I've shot at a target, and I've calculated my standard deviations in the x and y directions as $ sigma_x $ and $ sigma_y $ respectively from their variances, and I have also calculated the standard deviation of the root of the sums of their squares (the magnitude of the distance from the origin/bull's eye) as $sigma_r$. Now I know that these values are deviations around the mean value of each variable, which characterizes my shot grouping. I'm seeking to find my standard deviation away from the origin as well, i.e. I'm wanting to know how far I'm deviating away from the center of the target versus how far I'm deviating from the calculated center of my grouping. Would this value just be the calculation of the $sigma^2$ and $sigma$ around a mean of 0 in all the variables so that I have a measure of deviation from perfect, or is this the incorrect way to go about the problem. All standard deviations used are population standard deviations, e.g. $$ sigma^2 = sum_i=1^n left ( frac1n(x_i - mu)^2 right ) ;; ; ; ; sigma = sqrtsigma^2 $$ where in the case in question, $mu$ would be taken to be 0, leaving just the sums of the squares as the variance.










share|cite|improve this question









$endgroup$




I'm collecting data from x and y axis offset from origin of the impact points of rounds I've shot at a target, and I've calculated my standard deviations in the x and y directions as $ sigma_x $ and $ sigma_y $ respectively from their variances, and I have also calculated the standard deviation of the root of the sums of their squares (the magnitude of the distance from the origin/bull's eye) as $sigma_r$. Now I know that these values are deviations around the mean value of each variable, which characterizes my shot grouping. I'm seeking to find my standard deviation away from the origin as well, i.e. I'm wanting to know how far I'm deviating away from the center of the target versus how far I'm deviating from the calculated center of my grouping. Would this value just be the calculation of the $sigma^2$ and $sigma$ around a mean of 0 in all the variables so that I have a measure of deviation from perfect, or is this the incorrect way to go about the problem. All standard deviations used are population standard deviations, e.g. $$ sigma^2 = sum_i=1^n left ( frac1n(x_i - mu)^2 right ) ;; ; ; ; sigma = sqrtsigma^2 $$ where in the case in question, $mu$ would be taken to be 0, leaving just the sums of the squares as the variance.







statistics






share|cite|improve this question













share|cite|improve this question











share|cite|improve this question




share|cite|improve this question










asked Nov 9 '14 at 6:12









Doryan MillerDoryan Miller

263112




263112











  • $begingroup$
    You seem to be interested in the two second moments about the origin, an important notion, though closely related to variance.
    $endgroup$
    – André Nicolas
    Nov 9 '14 at 6:17










  • $begingroup$
    I believe what I'm asking is if I have the correct idea for the calculation of the second moment about the origin.
    $endgroup$
    – Doryan Miller
    Nov 9 '14 at 6:24










  • $begingroup$
    Yes, it is right.
    $endgroup$
    – André Nicolas
    Nov 9 '14 at 6:26










  • $begingroup$
    Note the formula $E(X^2) = Var(X) + mu^2$, so you don't need to do a whole new calculation if you already know $mu$ and $sigma_x$.
    $endgroup$
    – user187373
    Nov 9 '14 at 7:49










  • $begingroup$
    If I'm reading that correctly, what I'm really just searching for, going by the name of the second moment around the origin, is merely the expected value of the square of my data, which is the first raw moment around the mean plus the square of said mean?
    $endgroup$
    – Doryan Miller
    Nov 9 '14 at 15:17
















  • $begingroup$
    You seem to be interested in the two second moments about the origin, an important notion, though closely related to variance.
    $endgroup$
    – André Nicolas
    Nov 9 '14 at 6:17










  • $begingroup$
    I believe what I'm asking is if I have the correct idea for the calculation of the second moment about the origin.
    $endgroup$
    – Doryan Miller
    Nov 9 '14 at 6:24










  • $begingroup$
    Yes, it is right.
    $endgroup$
    – André Nicolas
    Nov 9 '14 at 6:26










  • $begingroup$
    Note the formula $E(X^2) = Var(X) + mu^2$, so you don't need to do a whole new calculation if you already know $mu$ and $sigma_x$.
    $endgroup$
    – user187373
    Nov 9 '14 at 7:49










  • $begingroup$
    If I'm reading that correctly, what I'm really just searching for, going by the name of the second moment around the origin, is merely the expected value of the square of my data, which is the first raw moment around the mean plus the square of said mean?
    $endgroup$
    – Doryan Miller
    Nov 9 '14 at 15:17















$begingroup$
You seem to be interested in the two second moments about the origin, an important notion, though closely related to variance.
$endgroup$
– André Nicolas
Nov 9 '14 at 6:17




$begingroup$
You seem to be interested in the two second moments about the origin, an important notion, though closely related to variance.
$endgroup$
– André Nicolas
Nov 9 '14 at 6:17












$begingroup$
I believe what I'm asking is if I have the correct idea for the calculation of the second moment about the origin.
$endgroup$
– Doryan Miller
Nov 9 '14 at 6:24




$begingroup$
I believe what I'm asking is if I have the correct idea for the calculation of the second moment about the origin.
$endgroup$
– Doryan Miller
Nov 9 '14 at 6:24












$begingroup$
Yes, it is right.
$endgroup$
– André Nicolas
Nov 9 '14 at 6:26




$begingroup$
Yes, it is right.
$endgroup$
– André Nicolas
Nov 9 '14 at 6:26












$begingroup$
Note the formula $E(X^2) = Var(X) + mu^2$, so you don't need to do a whole new calculation if you already know $mu$ and $sigma_x$.
$endgroup$
– user187373
Nov 9 '14 at 7:49




$begingroup$
Note the formula $E(X^2) = Var(X) + mu^2$, so you don't need to do a whole new calculation if you already know $mu$ and $sigma_x$.
$endgroup$
– user187373
Nov 9 '14 at 7:49












$begingroup$
If I'm reading that correctly, what I'm really just searching for, going by the name of the second moment around the origin, is merely the expected value of the square of my data, which is the first raw moment around the mean plus the square of said mean?
$endgroup$
– Doryan Miller
Nov 9 '14 at 15:17




$begingroup$
If I'm reading that correctly, what I'm really just searching for, going by the name of the second moment around the origin, is merely the expected value of the square of my data, which is the first raw moment around the mean plus the square of said mean?
$endgroup$
– Doryan Miller
Nov 9 '14 at 15:17










1 Answer
1






active

oldest

votes


















0












$begingroup$

The line of reasoning in the question is correct.



Calculation of moments about the origin differ only from the former by setting $mu = 0$.






share|cite|improve this answer









$endgroup$












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    1 Answer
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    1 Answer
    1






    active

    oldest

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    active

    oldest

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    active

    oldest

    votes









    0












    $begingroup$

    The line of reasoning in the question is correct.



    Calculation of moments about the origin differ only from the former by setting $mu = 0$.






    share|cite|improve this answer









    $endgroup$

















      0












      $begingroup$

      The line of reasoning in the question is correct.



      Calculation of moments about the origin differ only from the former by setting $mu = 0$.






      share|cite|improve this answer









      $endgroup$















        0












        0








        0





        $begingroup$

        The line of reasoning in the question is correct.



        Calculation of moments about the origin differ only from the former by setting $mu = 0$.






        share|cite|improve this answer









        $endgroup$



        The line of reasoning in the question is correct.



        Calculation of moments about the origin differ only from the former by setting $mu = 0$.







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Mar 12 at 10:51









        Doryan MillerDoryan Miller

        263112




        263112



























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