seats by plan: a 21,443% spread

Breaking seats down by plan on saas-subscriptions, because the headline average is 51 and no segment is actually there.

• enterprise — mean 542, median 558 (150 rows)
• business — mean 69, median 69 (442 rows)
• team — mean 15, median 15 (800 rows)
• starter — mean 3, median 3 (1,108 rows)

Top to bottom that is 542 against 3, a spread of 21,442.7%. The pooled average is 51.

select plan,
  count(*)                                           as rows,
  round(avg(seats)::numeric, 2)                      as mean,
  percentile_cont(0.5) within group (order by seats) as median
from saas_subscriptions
group by 1
order by mean desc;

A spread that wide means the pooled number is not a summary, it is an artefact of the mix. Change the proportion of enterprise rows and the overall average moves without any individual group changing at all — which is how a metric goes up while every segment goes down.

Notice the mean and median columns disagree only slightly here. Always compute both in the group-by. The comparison between them per segment is free and tells you whether you are looking at a level difference or a tail difference.

This is the setup for Simpson's paradox — the case where every segment moves one way and the total moves the other.