Hi rtist, you almost solve the problem.
From the mean equation, I can get alpha/beta=17/3. And we have another variance equation. I stuck here because the beta distribution is not like the normal distribution,if we know the SD, we get the 95% C.I.,and vice versa. But how can I get the beta variance from a beta 95% probability interval? And without the variance value,I can't not solve the second equation.
I tried a lot combinations: e.g. alpha=17,beta=3, the mean is ok,but the variance is [0.80,0.90],approximately.It doesn't fit the requirement.
