Q&A for professional and enthusiast programmers
SELECT AVG(u1.Reputation) FROM Users u1 WHERE u1.Id IN (SELECT DISTINCT u.Id FROM Posts p INNER JOIN Users u ON p.OwnerUserId = u.Id INNER JOIN PostTags pt ON p.Id = pt.PostId INNER JOIN Tags t ON pt.TagId = t.Id WHERE p.PostTypeId = 1 )