How many businesses in Arizona having an average review less than 3 stars?
businesses in Arizona refer to business_id where state = 'Arizona'; average review less than 3 stars refers to AVG(review_stars) < 3.0;
SELECT COUNT(business_id) FROM Business WHERE business_id IN ( SELECT DISTINCT T1.business_id FROM Business AS T1 INNER JOIN Reviews AS T2 ON T1.business_id = T2.business_id WHERE T1.state = 'AZ' GROUP BY T1.business_id HAVING SUM(T2.review_stars) / COUNT(T2.user_id) < 3 )