Finding an estimator for a binomial parameter using the method of moments












0












$begingroup$


A random variable subject to binomial distribution $B(100,p)$.Find estimator of $p$ using method of moment.The values $x :14,13,17,15,20,25,13,22$?



I got :



$$Ex=np=frac{139}8$$
$$Vx=np (1-p)=frac{sum(x-Ex)^2}8=141.875/8$$



$$1-p=frac{141.875}{139}$$



$$p=-0.021$$



It's negative so I think it's not correct. Can you help me to solve this?






probability







share|cite|improve this question











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  • 1




    $begingroup$
    please, show your work
    $endgroup$
    – Martín Vacas Vignolo
    Dec 28 '18 at 5:27






  • 1




    $begingroup$
    Here's a MathJax tutorial :)
    $endgroup$
    – Shaun
    Dec 28 '18 at 5:59






  • 1




    $begingroup$
    You know $np=frac{139}8$ and $n=100$,so $p=ldots $
    $endgroup$
    – Thomas Shelby
    Dec 28 '18 at 6:01










  • $begingroup$
    So I do not need to find Vx? So p=0.17375?why we Do not find estimator of n?
    $endgroup$
    – Monika_j22
    Dec 28 '18 at 6:49


















0












$begingroup$


A random variable subject to binomial distribution $B(100,p)$.Find estimator of $p$ using method of moment.The values $x :14,13,17,15,20,25,13,22$?



I got :



$$Ex=np=frac{139}8$$
$$Vx=np (1-p)=frac{sum(x-Ex)^2}8=141.875/8$$



$$1-p=frac{141.875}{139}$$



$$p=-0.021$$



It's negative so I think it's not correct. Can you help me to solve this?






probability







share|cite|improve this question











$endgroup$








  • 1




    $begingroup$
    please, show your work
    $endgroup$
    – Martín Vacas Vignolo
    Dec 28 '18 at 5:27






  • 1




    $begingroup$
    Here's a MathJax tutorial :)
    $endgroup$
    – Shaun
    Dec 28 '18 at 5:59






  • 1




    $begingroup$
    You know $np=frac{139}8$ and $n=100$,so $p=ldots $
    $endgroup$
    – Thomas Shelby
    Dec 28 '18 at 6:01










  • $begingroup$
    So I do not need to find Vx? So p=0.17375?why we Do not find estimator of n?
    $endgroup$
    – Monika_j22
    Dec 28 '18 at 6:49
















0












0








0





$begingroup$


A random variable subject to binomial distribution $B(100,p)$.Find estimator of $p$ using method of moment.The values $x :14,13,17,15,20,25,13,22$?



I got :



$$Ex=np=frac{139}8$$
$$Vx=np (1-p)=frac{sum(x-Ex)^2}8=141.875/8$$



$$1-p=frac{141.875}{139}$$



$$p=-0.021$$



It's negative so I think it's not correct. Can you help me to solve this?






probability







share|cite|improve this question











$endgroup$




A random variable subject to binomial distribution $B(100,p)$.Find estimator of $p$ using method of moment.The values $x :14,13,17,15,20,25,13,22$?



I got :



$$Ex=np=frac{139}8$$
$$Vx=np (1-p)=frac{sum(x-Ex)^2}8=141.875/8$$



$$1-p=frac{141.875}{139}$$



$$p=-0.021$$



It's negative so I think it's not correct. Can you help me to solve this?






probability




probability






share|cite|improve this question















share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Dec 28 '18 at 9:20









Jean Marie

29.9k42051




29.9k42051










asked Dec 28 '18 at 5:15









Monika_j22Monika_j22

61




61








  • 1




    $begingroup$
    please, show your work
    $endgroup$
    – Martín Vacas Vignolo
    Dec 28 '18 at 5:27






  • 1




    $begingroup$
    Here's a MathJax tutorial :)
    $endgroup$
    – Shaun
    Dec 28 '18 at 5:59






  • 1




    $begingroup$
    You know $np=frac{139}8$ and $n=100$,so $p=ldots $
    $endgroup$
    – Thomas Shelby
    Dec 28 '18 at 6:01










  • $begingroup$
    So I do not need to find Vx? So p=0.17375?why we Do not find estimator of n?
    $endgroup$
    – Monika_j22
    Dec 28 '18 at 6:49
















  • 1




    $begingroup$
    please, show your work
    $endgroup$
    – Martín Vacas Vignolo
    Dec 28 '18 at 5:27






  • 1




    $begingroup$
    Here's a MathJax tutorial :)
    $endgroup$
    – Shaun
    Dec 28 '18 at 5:59






  • 1




    $begingroup$
    You know $np=frac{139}8$ and $n=100$,so $p=ldots $
    $endgroup$
    – Thomas Shelby
    Dec 28 '18 at 6:01










  • $begingroup$
    So I do not need to find Vx? So p=0.17375?why we Do not find estimator of n?
    $endgroup$
    – Monika_j22
    Dec 28 '18 at 6:49










1




1




$begingroup$
please, show your work
$endgroup$
– Martín Vacas Vignolo
Dec 28 '18 at 5:27




$begingroup$
please, show your work
$endgroup$
– Martín Vacas Vignolo
Dec 28 '18 at 5:27




1




1




$begingroup$
Here's a MathJax tutorial :)
$endgroup$
– Shaun
Dec 28 '18 at 5:59




$begingroup$
Here's a MathJax tutorial :)
$endgroup$
– Shaun
Dec 28 '18 at 5:59




1




1




$begingroup$
You know $np=frac{139}8$ and $n=100$,so $p=ldots $
$endgroup$
– Thomas Shelby
Dec 28 '18 at 6:01




$begingroup$
You know $np=frac{139}8$ and $n=100$,so $p=ldots $
$endgroup$
– Thomas Shelby
Dec 28 '18 at 6:01












$begingroup$
So I do not need to find Vx? So p=0.17375?why we Do not find estimator of n?
$endgroup$
– Monika_j22
Dec 28 '18 at 6:49






$begingroup$
So I do not need to find Vx? So p=0.17375?why we Do not find estimator of n?
$endgroup$
– Monika_j22
Dec 28 '18 at 6:49












1 Answer
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$begingroup$

$n=100$ has been given to you in the question, there is only one unknown parameter $p$ and we can get an estimator from the first moment.



We can recover $hat{p}$ by



$$100hat{p} = frac18 sum_{i=1}^8 x_i$$






share|cite|improve this answer









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    1












    $begingroup$

    $n=100$ has been given to you in the question, there is only one unknown parameter $p$ and we can get an estimator from the first moment.



    We can recover $hat{p}$ by



    $$100hat{p} = frac18 sum_{i=1}^8 x_i$$






    share|cite|improve this answer









    $endgroup$


















      1












      $begingroup$

      $n=100$ has been given to you in the question, there is only one unknown parameter $p$ and we can get an estimator from the first moment.



      We can recover $hat{p}$ by



      $$100hat{p} = frac18 sum_{i=1}^8 x_i$$






      share|cite|improve this answer









      $endgroup$
















        1












        1








        1





        $begingroup$

        $n=100$ has been given to you in the question, there is only one unknown parameter $p$ and we can get an estimator from the first moment.



        We can recover $hat{p}$ by



        $$100hat{p} = frac18 sum_{i=1}^8 x_i$$






        share|cite|improve this answer









        $endgroup$



        $n=100$ has been given to you in the question, there is only one unknown parameter $p$ and we can get an estimator from the first moment.



        We can recover $hat{p}$ by



        $$100hat{p} = frac18 sum_{i=1}^8 x_i$$







        share|cite|improve this answer












        share|cite|improve this answer



        share|cite|improve this answer










        answered Dec 28 '18 at 7:51









        Siong Thye GohSiong Thye Goh

        101k1466118




        101k1466118






























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