Field note · July 25, 2025
ab-test-checkout.device: 3 values, 100.0% in the top three
3 values with 54.7% concentrated in one of them, and what that does to every chart downstream.
Distribution of device on ab-test-checkout, because every chart built on it inherits this shape.
mobile— 3,284 rows, 54.7%desktop— 2,308 rows, 38.5%tablet— 408 rows, 6.8%
The top three take 100.0% between them. With only 3 values there is no tail to worry about, which makes this a genuinely easy column to chart.
select device,
count(*) as rows,
round(100.0 * count(*) / sum(count(*)) over (), 1) as pct,
round(avg(revenue_usd)::numeric, 2) as avg_revenue_usd
from ab_test_checkout
group by 1
order by rows desc;The second column is the one that matters. Share of rows tells you what is common; avg_revenue_usd tells you whether the common thing is the important thing. They disagree more often than not, and a chart that shows only the first is answering the easier question.
Decide what happens to the tail before you plot it. "Other" as an explicit bucket is honest; twelve slivers is not, and neither is silently taking the top eight.