Hi James,
Just updated this post, I read the requirement wrong earlier. (12/16/2015 1:26 pm EST)
In the Universe, create an object called Product Group with the below formula and in the Report, create a Prompt on that object using the Inlist operator.
Case
When product_mobiles in ('iPhone 4','iPhone 5','iPhone 6') Then 'Apple Phones'
When product_mobiles in ('Galaxy 4','Galaxy 5') Then 'Samsung Phones'
When product_mobiles in ('Sensation','Desire','One') Then 'HTC'
When product_mobiles in ('iPod','iWatch') Then 'Other Apple Products'
When product_mobiles in ('Galaxy Tab') Then 'Other Samsung Products'
Else 'Others'
End
Hope that helps.
Thanks,
Mahboob Mohammed