Average IFs multiple criteria issues

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!

If you're really using Excel 2013, you have the IFERROR function. You could simplify your formulas by using it. For example, you have

AV5: =IF(ISERROR(AVERAGEIFS($F5:$AK8,$F5:$AK8,">3", $F5:$AK8,"<6")),"",AVERAGEIFS($F5:$AK8,$F5:$AK8,">3", $F5:$AK8,"<6"))

which could be simplified to

AV5: =IFERROR(AVERAGEIFS($F5:$AK8,$F5:$AK8,">3",$F5:$AK8,"<6"),"")

For that matter, you could use some clever text parsing on AV2:AX2 to get the range bounds, e.g.,

AV5: =IFERROR(AVERAGEIFS($F5:$AK8,$F5:$AK8,">="&REPLACE(LEFT(AV$2,FIND("-",AV$2)-1),1,FIND(CHAR(10),AV$2),""), $F5:$AK8,"<="&REPLACE(LEFT(AV$2,FIND("s"&CHAR(10),AV$2)-1),1,FIND("-",AV$2),"")),"")

Now the problem with the formula in AV15. What you have is

AV15: =IF(ISERROR(AVERAGEIFS($F13:$AK16,$F13:$AK16,">3", $F13:$AK16,"<6")),"",AVERAGEIFS($F13:$AK16,$F13:$AK16,">3",$F13:$AK16,"<6"))

however, it looks to me that your AVERAGEIFS ranges are referring to the wrong rows. I believe this formula should be

AV15: =IFERROR(AVERAGEIFS($F15:$AK18,$F15:$AK18,">3",$F15:$AK18,"<6"),"")

Similarly, your AV40 formula should be

AV40: =IFERROR(AVERAGEIFS($F40:$AK43,$F40:$AK43,">3",$F40:$AK43,"<6"),"")

Hi Hrlngrv,
Thanks for the assistance.
Your suggestion for av15 is the right answer to a different question.
The goal of the formula in av15 is to take the averages in the blue area (Post-treatment) only if their corresponding Pretreatment value (in yellow area) was within the range stated in Av2, Av3, Av 4.
Can you help with this?

Thanks Bob! That did the trick.
I appreciate your assistance.