Другое решение:
=ArrayFormula({"Average";(ArrayFormula(mmult(N(array_constrain(ArrayFormula(IFERROR(SPLIT(A4:A8,","))),MATCH(2,1/(A4:A8<>""),1),5)),sequence(Columns(ArrayFormula(IFERROR(SPLIT(A4:A8,",")))),1)^0)/mmult(N(array_constrain(if(ArrayFormula(IFERROR(SPLIT(A4:A8,",")))>0,1,0),MATCH(2,1/(A4:A8<>""),1),5)),sequence(columns(ArrayFormula(IFERROR(SPLIT(A4:A8,",")))),1)^0)))/$B$1})
введите описание изображения здесь