Average IFs multiple criteria issues

[bob33]

In the attached sample, in the pink cells, I'm attempting to take the average values of the blue shaded area depending on the values in the yellow shaded area.
For example, for all Pretreatment values between a range, what is the average Treatment values associated with them.
I think I have some of the pink Pretreatment values right but not the Treatment values.

I appreciate the help!