SELECT avg(T1.HS) FROM player AS T1 JOIN tryout AS T2 ON T1.pID  =  T2.pID WHERE T2.decision  =  'no'
Find the average hours for the students whose tryout decision is no.
[Schema (values) (types)]: | soccer_2 |  College : cname (text) , state (text) , enr (text) | Player : pid (text) , pname (text) , ycard (text) , hs (number) | Tryout : pid (text) , cname (text) , ppos (text) , decision (number);