Q&A with average

I was wondering whether it's possible to ask power bi an average question. This question works:

"all student patient adult greater than 4" (shows all the students who have more than 4 adult patients)

but the average doesn't seem to be possible:

"all student less than patient adult average"

to get the list of students who have less than the average number of adult patients. There isn't an average column, just students and total of various types of patient.

thanks,

Alistair