Beta distribution: find the parameter $alpha$ of $mathcal{B}e(alpha,frac{1}{3})$












0












$begingroup$


I have this variable with beta distribution : $Y sim mathcal{B}e(alpha,frac{1}{3})$.



I have to find the value of $alpha$ such as :
$P(Y leq 0.416) =0.2 $



Formally for $alpha geq 0$ , $beta geq 0$ and $0 leq y leq 1$ the CDF function of $Y$ at 0.416 is:



$P(Y leq 0.416) = frac{Gamma(alpha + beta)}{Gamma(alpha)Gamma(beta)} int_0^{0.416} t^{alpha-1} (1-t)^{beta-1} dt=0.2$



I am not sure how to proceed. Thanks for the help in advance!!










share|cite|improve this question









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    0












    $begingroup$


    I have this variable with beta distribution : $Y sim mathcal{B}e(alpha,frac{1}{3})$.



    I have to find the value of $alpha$ such as :
    $P(Y leq 0.416) =0.2 $



    Formally for $alpha geq 0$ , $beta geq 0$ and $0 leq y leq 1$ the CDF function of $Y$ at 0.416 is:



    $P(Y leq 0.416) = frac{Gamma(alpha + beta)}{Gamma(alpha)Gamma(beta)} int_0^{0.416} t^{alpha-1} (1-t)^{beta-1} dt=0.2$



    I am not sure how to proceed. Thanks for the help in advance!!










    share|cite|improve this question









    $endgroup$















      0












      0








      0





      $begingroup$


      I have this variable with beta distribution : $Y sim mathcal{B}e(alpha,frac{1}{3})$.



      I have to find the value of $alpha$ such as :
      $P(Y leq 0.416) =0.2 $



      Formally for $alpha geq 0$ , $beta geq 0$ and $0 leq y leq 1$ the CDF function of $Y$ at 0.416 is:



      $P(Y leq 0.416) = frac{Gamma(alpha + beta)}{Gamma(alpha)Gamma(beta)} int_0^{0.416} t^{alpha-1} (1-t)^{beta-1} dt=0.2$



      I am not sure how to proceed. Thanks for the help in advance!!










      share|cite|improve this question









      $endgroup$




      I have this variable with beta distribution : $Y sim mathcal{B}e(alpha,frac{1}{3})$.



      I have to find the value of $alpha$ such as :
      $P(Y leq 0.416) =0.2 $



      Formally for $alpha geq 0$ , $beta geq 0$ and $0 leq y leq 1$ the CDF function of $Y$ at 0.416 is:



      $P(Y leq 0.416) = frac{Gamma(alpha + beta)}{Gamma(alpha)Gamma(beta)} int_0^{0.416} t^{alpha-1} (1-t)^{beta-1} dt=0.2$



      I am not sure how to proceed. Thanks for the help in advance!!







      probability integration probability-distributions gamma-function beta-function






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      asked Dec 13 '18 at 15:04









      andrewandrew

      698




      698






















          1 Answer
          1






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          1












          $begingroup$

          Maple gives the CDF for $mathcal{B}e(alpha,beta)$ as
          $$ {frac {Gamma left( alpha+beta right) {y}^{alpha}
          {mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}}{Gamma left(
          alpha right) Gamma left( beta right) alpha}}
          $$

          In any case, you need to use numerical methods to solve $F(0.416) = 0.2$.
          Maple says $alpha = 0.8563203833$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            The question is stated as though an analytical solution is expected...but I agree that numerical methods are the way to proceed here.
            $endgroup$
            – Math1000
            Dec 13 '18 at 15:13










          • $begingroup$
            thank you very much for the kind answer. But i don't understand the meaning of this quantity: ${mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}$. And how did you obtain the value of $alpha$? Thank you in advance @Robert Israel
            $endgroup$
            – andrew
            Dec 13 '18 at 15:25












          • $begingroup$
            Can i get a solution with the software R?
            $endgroup$
            – andrew
            Dec 13 '18 at 16:40










          • $begingroup$
            ${}_2F_1(a,b; c; z)$ is a Gaussian hypergeometric function. The value of $alpha$ was obtained using a numerical solver (fsolve in Maple).
            $endgroup$
            – Robert Israel
            Dec 13 '18 at 18:55











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          1 Answer
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          active

          oldest

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          1 Answer
          1






          active

          oldest

          votes









          active

          oldest

          votes






          active

          oldest

          votes









          1












          $begingroup$

          Maple gives the CDF for $mathcal{B}e(alpha,beta)$ as
          $$ {frac {Gamma left( alpha+beta right) {y}^{alpha}
          {mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}}{Gamma left(
          alpha right) Gamma left( beta right) alpha}}
          $$

          In any case, you need to use numerical methods to solve $F(0.416) = 0.2$.
          Maple says $alpha = 0.8563203833$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            The question is stated as though an analytical solution is expected...but I agree that numerical methods are the way to proceed here.
            $endgroup$
            – Math1000
            Dec 13 '18 at 15:13










          • $begingroup$
            thank you very much for the kind answer. But i don't understand the meaning of this quantity: ${mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}$. And how did you obtain the value of $alpha$? Thank you in advance @Robert Israel
            $endgroup$
            – andrew
            Dec 13 '18 at 15:25












          • $begingroup$
            Can i get a solution with the software R?
            $endgroup$
            – andrew
            Dec 13 '18 at 16:40










          • $begingroup$
            ${}_2F_1(a,b; c; z)$ is a Gaussian hypergeometric function. The value of $alpha$ was obtained using a numerical solver (fsolve in Maple).
            $endgroup$
            – Robert Israel
            Dec 13 '18 at 18:55
















          1












          $begingroup$

          Maple gives the CDF for $mathcal{B}e(alpha,beta)$ as
          $$ {frac {Gamma left( alpha+beta right) {y}^{alpha}
          {mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}}{Gamma left(
          alpha right) Gamma left( beta right) alpha}}
          $$

          In any case, you need to use numerical methods to solve $F(0.416) = 0.2$.
          Maple says $alpha = 0.8563203833$.






          share|cite|improve this answer









          $endgroup$













          • $begingroup$
            The question is stated as though an analytical solution is expected...but I agree that numerical methods are the way to proceed here.
            $endgroup$
            – Math1000
            Dec 13 '18 at 15:13










          • $begingroup$
            thank you very much for the kind answer. But i don't understand the meaning of this quantity: ${mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}$. And how did you obtain the value of $alpha$? Thank you in advance @Robert Israel
            $endgroup$
            – andrew
            Dec 13 '18 at 15:25












          • $begingroup$
            Can i get a solution with the software R?
            $endgroup$
            – andrew
            Dec 13 '18 at 16:40










          • $begingroup$
            ${}_2F_1(a,b; c; z)$ is a Gaussian hypergeometric function. The value of $alpha$ was obtained using a numerical solver (fsolve in Maple).
            $endgroup$
            – Robert Israel
            Dec 13 '18 at 18:55














          1












          1








          1





          $begingroup$

          Maple gives the CDF for $mathcal{B}e(alpha,beta)$ as
          $$ {frac {Gamma left( alpha+beta right) {y}^{alpha}
          {mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}}{Gamma left(
          alpha right) Gamma left( beta right) alpha}}
          $$

          In any case, you need to use numerical methods to solve $F(0.416) = 0.2$.
          Maple says $alpha = 0.8563203833$.






          share|cite|improve this answer









          $endgroup$



          Maple gives the CDF for $mathcal{B}e(alpha,beta)$ as
          $$ {frac {Gamma left( alpha+beta right) {y}^{alpha}
          {mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}}{Gamma left(
          alpha right) Gamma left( beta right) alpha}}
          $$

          In any case, you need to use numerical methods to solve $F(0.416) = 0.2$.
          Maple says $alpha = 0.8563203833$.







          share|cite|improve this answer












          share|cite|improve this answer



          share|cite|improve this answer










          answered Dec 13 '18 at 15:12









          Robert IsraelRobert Israel

          325k23214468




          325k23214468












          • $begingroup$
            The question is stated as though an analytical solution is expected...but I agree that numerical methods are the way to proceed here.
            $endgroup$
            – Math1000
            Dec 13 '18 at 15:13










          • $begingroup$
            thank you very much for the kind answer. But i don't understand the meaning of this quantity: ${mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}$. And how did you obtain the value of $alpha$? Thank you in advance @Robert Israel
            $endgroup$
            – andrew
            Dec 13 '18 at 15:25












          • $begingroup$
            Can i get a solution with the software R?
            $endgroup$
            – andrew
            Dec 13 '18 at 16:40










          • $begingroup$
            ${}_2F_1(a,b; c; z)$ is a Gaussian hypergeometric function. The value of $alpha$ was obtained using a numerical solver (fsolve in Maple).
            $endgroup$
            – Robert Israel
            Dec 13 '18 at 18:55


















          • $begingroup$
            The question is stated as though an analytical solution is expected...but I agree that numerical methods are the way to proceed here.
            $endgroup$
            – Math1000
            Dec 13 '18 at 15:13










          • $begingroup$
            thank you very much for the kind answer. But i don't understand the meaning of this quantity: ${mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}$. And how did you obtain the value of $alpha$? Thank you in advance @Robert Israel
            $endgroup$
            – andrew
            Dec 13 '18 at 15:25












          • $begingroup$
            Can i get a solution with the software R?
            $endgroup$
            – andrew
            Dec 13 '18 at 16:40










          • $begingroup$
            ${}_2F_1(a,b; c; z)$ is a Gaussian hypergeometric function. The value of $alpha$ was obtained using a numerical solver (fsolve in Maple).
            $endgroup$
            – Robert Israel
            Dec 13 '18 at 18:55
















          $begingroup$
          The question is stated as though an analytical solution is expected...but I agree that numerical methods are the way to proceed here.
          $endgroup$
          – Math1000
          Dec 13 '18 at 15:13




          $begingroup$
          The question is stated as though an analytical solution is expected...but I agree that numerical methods are the way to proceed here.
          $endgroup$
          – Math1000
          Dec 13 '18 at 15:13












          $begingroup$
          thank you very much for the kind answer. But i don't understand the meaning of this quantity: ${mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}$. And how did you obtain the value of $alpha$? Thank you in advance @Robert Israel
          $endgroup$
          – andrew
          Dec 13 '18 at 15:25






          $begingroup$
          thank you very much for the kind answer. But i don't understand the meaning of this quantity: ${mbox{$_2$F$_1$}(alpha,1-beta;,1+alpha;,y)}$. And how did you obtain the value of $alpha$? Thank you in advance @Robert Israel
          $endgroup$
          – andrew
          Dec 13 '18 at 15:25














          $begingroup$
          Can i get a solution with the software R?
          $endgroup$
          – andrew
          Dec 13 '18 at 16:40




          $begingroup$
          Can i get a solution with the software R?
          $endgroup$
          – andrew
          Dec 13 '18 at 16:40












          $begingroup$
          ${}_2F_1(a,b; c; z)$ is a Gaussian hypergeometric function. The value of $alpha$ was obtained using a numerical solver (fsolve in Maple).
          $endgroup$
          – Robert Israel
          Dec 13 '18 at 18:55




          $begingroup$
          ${}_2F_1(a,b; c; z)$ is a Gaussian hypergeometric function. The value of $alpha$ was obtained using a numerical solver (fsolve in Maple).
          $endgroup$
          – Robert Israel
          Dec 13 '18 at 18:55


















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