user: Question: What round on average was a Defensive Tackle selected?
Columns: ['Round', 'Pick #', 'Overall', 'Name', 'Position', 'College']
Types: ['real', 'real', 'real', 'text', 'text', 'text']
Sample row: [2.0, 5.0, 31.0, 'Leo Carroll', 'Defensive End', 'San Diego State']
SQL:

assistant: SELECT AVG("Round") FROM "Table" WHERE "Position" = 'Defensive Tackle';