select up.university,count(qpd.question_id)/count(distinct qpd.device_id) as avg_answer_cnt from user_profile as up inner join question_practice_detail as qpd on up.device_id = qpd.device_id group by up.university
select up.university,count(qpd.question_id)/count(distinct qpd.device_id) as avg_answer_cnt from user_profile as up inner join question_practice_detail as qpd on up.device_id = qpd.device_id group by up.university