In my lame search, I have not been able determine if a FOX SQL statement with a GROUP BY clause can be optimized using indexes (rushmore). Is it possible?

I have a large set of data created using the SET COVERAGE statement, and I am trying to aggregate the duration to find the lines that consume the maximum time. Currently the SQL statement is taking around 5+ minutes. I was thinking that if an indexes on the Method column would help in speeding up the aggregation.