You shouldn't have to use MDX to get the desired outcome. Creating a calculated field similar to the following should work:
if [Unit Sales]>=[Parameter 3] then 'Good' else 'Average' end
Hope this helps!
I´m new with Tabular Models. How you connect to them? using the SSAS Connector for Tableau?, in that case, the queries sent from Tableau to the data engine are MDX? (Even if Tabular Models are defined in DAX).
Can you help me to understand or giving some pointers to some documentation about that?