What is causing a scope parameter error in my SSRS

问题:

Why am I getting this error in my chart? (Chart Image)

I am using this expression in the chart:

Series:

=Sum(Fields!Mins_Att.Value)/Sum(Fields!Mins_Poss.Value)

Series 1: 

=Sum(Fields!Mins_Att.Value, 
         "Chart2_CategoryGroup2")/Sum(Fields!Mins_Poss.Value, "Chart2_CategoryGroup2")

and I am getting this error:

The Y expression for the Chart has a scope parameter that is not valid for an aggregate function. The scope parameter must be set to a string constant that is equal the name of group, data region or name of dataset.

回答1:

The scope of "Chart2_CategoryGroup2" doesn't exist in the report.