Family of densities on [0,1] with strictly positive density at zero












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I am looking for a parameterized family of probability densities on the unit interval, which all share a strictly positive density at zero. Ideally, they could be parameterized by some parameter $lambda$, such that a higher $lambda$ implies first order stochastic dominance. Is there something like this, or maybe close to it?



Thanks!










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    $begingroup$


    I am looking for a parameterized family of probability densities on the unit interval, which all share a strictly positive density at zero. Ideally, they could be parameterized by some parameter $lambda$, such that a higher $lambda$ implies first order stochastic dominance. Is there something like this, or maybe close to it?



    Thanks!










    share|cite|improve this question











    $endgroup$















      1












      1








      1





      $begingroup$


      I am looking for a parameterized family of probability densities on the unit interval, which all share a strictly positive density at zero. Ideally, they could be parameterized by some parameter $lambda$, such that a higher $lambda$ implies first order stochastic dominance. Is there something like this, or maybe close to it?



      Thanks!










      share|cite|improve this question











      $endgroup$




      I am looking for a parameterized family of probability densities on the unit interval, which all share a strictly positive density at zero. Ideally, they could be parameterized by some parameter $lambda$, such that a higher $lambda$ implies first order stochastic dominance. Is there something like this, or maybe close to it?



      Thanks!







      probability integration probability-distributions






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      edited Jan 18 at 10:14









      md2perpe

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      asked Jan 15 at 0:55









      user509037user509037

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          You could form a density like this using a mixture of Beta distributions. For example, we could take a mixture of a uniform distribution (to give non-zero density at all points) and another Beta distribution parameterised with $lambda$ as the mean. This gives the general form:



          $$f_X(x) = phi + (1-phi) cdot frac{x^{lambda kappa-1} (1-x)^{(1-lambda) kappa -1}}{B(lambda kappa, (1-lambda) kappa)} quad quad quad text{for all } 0 leqslant x leqslant 1.$$



          where $0 < phi < 1$ and $kappa >0$. This distribution has non-zero density at all points and higher values of $lambda$ give higher values (in the sense of first-order stochastic dominance). In particular, it has mean:



          $$mathbb{E}(X) = frac{phi}{2} + (1-phi) lambda.$$






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            $begingroup$

            You could form a density like this using a mixture of Beta distributions. For example, we could take a mixture of a uniform distribution (to give non-zero density at all points) and another Beta distribution parameterised with $lambda$ as the mean. This gives the general form:



            $$f_X(x) = phi + (1-phi) cdot frac{x^{lambda kappa-1} (1-x)^{(1-lambda) kappa -1}}{B(lambda kappa, (1-lambda) kappa)} quad quad quad text{for all } 0 leqslant x leqslant 1.$$



            where $0 < phi < 1$ and $kappa >0$. This distribution has non-zero density at all points and higher values of $lambda$ give higher values (in the sense of first-order stochastic dominance). In particular, it has mean:



            $$mathbb{E}(X) = frac{phi}{2} + (1-phi) lambda.$$






            share|cite|improve this answer









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              $begingroup$

              You could form a density like this using a mixture of Beta distributions. For example, we could take a mixture of a uniform distribution (to give non-zero density at all points) and another Beta distribution parameterised with $lambda$ as the mean. This gives the general form:



              $$f_X(x) = phi + (1-phi) cdot frac{x^{lambda kappa-1} (1-x)^{(1-lambda) kappa -1}}{B(lambda kappa, (1-lambda) kappa)} quad quad quad text{for all } 0 leqslant x leqslant 1.$$



              where $0 < phi < 1$ and $kappa >0$. This distribution has non-zero density at all points and higher values of $lambda$ give higher values (in the sense of first-order stochastic dominance). In particular, it has mean:



              $$mathbb{E}(X) = frac{phi}{2} + (1-phi) lambda.$$






              share|cite|improve this answer









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                $begingroup$

                You could form a density like this using a mixture of Beta distributions. For example, we could take a mixture of a uniform distribution (to give non-zero density at all points) and another Beta distribution parameterised with $lambda$ as the mean. This gives the general form:



                $$f_X(x) = phi + (1-phi) cdot frac{x^{lambda kappa-1} (1-x)^{(1-lambda) kappa -1}}{B(lambda kappa, (1-lambda) kappa)} quad quad quad text{for all } 0 leqslant x leqslant 1.$$



                where $0 < phi < 1$ and $kappa >0$. This distribution has non-zero density at all points and higher values of $lambda$ give higher values (in the sense of first-order stochastic dominance). In particular, it has mean:



                $$mathbb{E}(X) = frac{phi}{2} + (1-phi) lambda.$$






                share|cite|improve this answer









                $endgroup$



                You could form a density like this using a mixture of Beta distributions. For example, we could take a mixture of a uniform distribution (to give non-zero density at all points) and another Beta distribution parameterised with $lambda$ as the mean. This gives the general form:



                $$f_X(x) = phi + (1-phi) cdot frac{x^{lambda kappa-1} (1-x)^{(1-lambda) kappa -1}}{B(lambda kappa, (1-lambda) kappa)} quad quad quad text{for all } 0 leqslant x leqslant 1.$$



                where $0 < phi < 1$ and $kappa >0$. This distribution has non-zero density at all points and higher values of $lambda$ give higher values (in the sense of first-order stochastic dominance). In particular, it has mean:



                $$mathbb{E}(X) = frac{phi}{2} + (1-phi) lambda.$$







                share|cite|improve this answer












                share|cite|improve this answer



                share|cite|improve this answer










                answered Jan 15 at 3:31









                BenBen

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