Conversion
Funnel drop-off
Also called step abandonment.
Funnel drop-off is the share of people who complete step n but not step n+1. It points at the single place a path leaks.
How it is measured
For each pair of adjacent steps, subtract the count at the second from the count at the first, then divide by the first. Use the same window for both.
In Tarsier this is simple arithmetic on two event counts for the same dates.
Worked example
A repair-booking funnel has 900 at pick-a-device, 610 at describe-the-problem, 540 at choose-a-slot and 310 at confirm. The slot-to-confirm drop-off is 43 percent, the worst by far.
Support learns the confirm page asks for a card number the shop does not need. They remove it and the step improves to 24 percent.
How it differs
Funnel drop-off compares two neighbours. A funnel is the whole path. Abandonment rate is the overall loss. A checkout step is the usual site of drop-off in shops.
Common errors
Reading drop-off on a step with tiny counts. Counting returning people twice. Using different windows for each step. Ignoring that people skip steps. Blaming copy before checking bugs.
In practice
Rank steps by drop-off times volume, and look at the top one with a real session on a phone.