Q&A for professional and enthusiast programmers
select dateadd(week,0, datediff(week,0, CreationDate)) week, sum(iif(ClosedDate <= CreationDate+3 /*and IsClosedAsDuplicate = 0*/, 1.0, 0))/count(*) closed from Posts where PostTypeId = 1 group by dateadd(week,0, datediff(week,0, CreationDate)) order by dateadd(week,0, datediff(week,0, CreationDate))