gamma VS inverse gamma distribution

[DW916]

Dear Johannes.

Could I ask a question about prior distribution? In practice, what is the difference between Gamma and Inverse Gamma distribution?

Thanks a lot!
Catherine

[jpfeifer]

It is mostly a conceptual difference. The inverse gamma distribution does not include 0, while the gamma distribution does. In practice, that does not matter much, because having a zero is a zero probability event in any case. Thus, the practical difference is that the two have somewhat different shapes. See the pictures in the right box at https://en.wikipedia.org/wiki/Inverse-gamma_distribution and https://en.wikipedia.org/wiki/Gamma_distribution