By way of explanation: the named formula 'assumption'
= IF( Case, CHOOSE( Case, Min, ML, Max ), tblPBS )
uses values written above each column, 'Case', to determine which region of the data table to select.
Case=0 returns the entire table.
= AVERAGEIFS( assumption tblPBS[Dev], .....................….....'Intersects the assumption and the development cost column'
...........................assumption tblPBS[Name], Part, .................'match the Name column to the Part in column A'
.........…………….assumption tblPBS[Cost Type], "System"), 'return only rows for which the cost type is system'
…. "" ) ........................................................................................'return blank if no part name is specified'