Question

I’m looking for a way to calculate a useful average for a given set of values which may contain huge spikes. (e.g 21, 54, 34, 14, 20, 300, 23 or 1, 1, 1, 1, 200, 1, 100) the spikes can throw things off when using the standard average calculation.

I looked into using the median but this doesn’t really give the desired result.

I would like to implement this in T-SQL

Any ideas?

Answer 1

This way you can take away the highest and the lowest 25 % before calculating the result.

declare @t table (col1 int)

insert @t
select 21 union all 
select 54 union all 
select 34 union all 
select 14 union all 
select 20 union all 
select 300 union all 
select 23 union all 
select 1 union all 
select 1 union all 
select 1 union all 
select 1 union all 
select 200 union all 
select 1 union all 
select 100


select avg(col1) from (
select top 67 percent col1 from (
select top 75 percent col1 from @t order by col1
) a order by col1 desc) b