user: Question: COunt the average Diameter (km) which has Ketian (Yenisey R.) main evil goddess.?
Columns: ['Name', 'Latitude', 'Longitude', 'Diameter (km)', 'Year named', 'Name origin']
Types: ['text', 'text', 'text', 'real', 'real', 'text']
Sample row: ['Aife Fossae', '67.0N', '131.0E', 280.0, 1997.0, 'Irish warrior deity.']
SQL:

assistant: SELECT AVG("Diameter (km)") FROM "Table" WHERE "Name origin" = 'Ketian (Yenisey R.) main evil goddess.';