Formula to return range based on criteria

[wd56]

Hi All

I am trying to figure out a formula that will return a range based on specific criteria. For example:

Criteria 1: Column A, Criteria 2: Column B. When both a fulfilled return A1:A15. I've attached a basic example, looking for a formula to return the range under the red column. Example 1.xlsx

Appreciate any help and thank you so much for your time and energy!

Edit: Using Microsoft® Excel® for Microsoft 365 MSO (Version 2302 Build 16.0.16130.20806) 64-bit if it matters

Edit 2: I updated the attachment with the exact details I am trying to work on, there is a new tab "Specific Example" which *crossed fingers* I have completely made generic. The focus is in rows 4 through 9, the "Median", "Fit range" and "Pop" columns. I have currently performed the range selections for each of them manually but I would like to automate the range selection in the median, countifs and count formula so that people can mess with the underlying population and the calculations update automatically