# How to define the bounds of Gamma distribution (a,b)

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Houda el 4 de Jun. de 2017
Comentada: Star Strider el 5 de Jun. de 2017
Hey everybody, I am looking for how to calculate the interval of the gamma density distribution when setting the priors in Bayesian estimation. For beta(a,b) the mean of X= E(X)=a/(a+b) and variance is V(X)=(a+b)/(a+b+1)(a+b)^2, as we define the mean and varaince from the common values in the literature I return and calculate a and b. Please for gamma (a,b) distribution with E(X)=0.74 and std(X)=0.0056 how to find a and b? Many thanks in advance.
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Star Strider el 4 de Jun. de 2017
The Wikipedia article on the Gamma distribution (link) indicates that:
gamma_mean = a*b;
gamma_var = a*b^2;
gamma_mean = 0.74
gamma_var = 0.0056^2 % Var is StDev^2
b = gamma_var/gamma_mean
a = gamma_mean/b
b =
4.2378e-05
a =
17462
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Houda el 4 de Jun. de 2017
Thanks a lot because I tried before to resolve this issue but with to not avail, thanks to you I found correct results as the autho, however, in many cases it was impossible. I attached the paper you can check by your self (table 2 P1274). take care.
Star Strider el 5 de Jun. de 2017
My pleasure.
I will look through the paper.

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