Show all artist names with an average exhibition attendance over 200.
SELECT T3.name FROM exhibition_record AS T1 JOIN exhibition AS T2 ON T1.exhibition_id  =  T2.exhibition_id JOIN artist AS T3 ON T3.artist_id  =  T2.artist_id GROUP BY T3.artist_id HAVING avg(T1.attendance)  >  200
200'den fazla ortalama sergi katılımıyla tüm sanatçı isimlerini gösterin.