user: Question: What is the couples name where the average is 15.9?
Columns: ['Rank by average', 'Place', 'Couple', 'Number of Dances', 'Total Points', 'Average']
Types: ['real', 'real', 'text', 'real', 'text', 'text']
Sample row: [1.0, 1.0, 'Ray & Maria', 11.0, '300.5', '27.3']
SQL:

assistant: SELECT "Couple" FROM "Table" WHERE "Average" = '15.9';