rates
Inspection paradox
A random arrival lands in a long gap.
You look at something at a random moment. You are more likely to catch it during a long interval than during a short one. The average you see is longer than the true average.
Buses arrive at uneven intervals. Check the gap you actually land in.
Short gaps are easy to miss. Long gaps are easy to hit.
The typical gap a random passenger experiences is longer than the average gap on the schedule.
The same effect appears with class sizes, hospital stays, or any process made of uneven intervals.
Sampling at a random moment over-samples the longer cases.