Dear Rick,
About the approximation for the median of a chi-square distribution that you recommend, (1-x)^3, I just wanted to ask you:
1. For which values of x does it apply? I guess that just for x<1, but please let me know if I'm wrong.
2. Is there a published paper (yours of from someone else) that stands after such an approximation?. This is because I would like to use such a formula in a document that I'm working in, but I would like to have a formal reference about it.

Thanks in advance for your kind repply,