Engagement
Engagement rate
Also called engaged session rate.
Engagement rate is the share of sessions that met the engagement rule. Under a matching rule it is the inverse of bounce rate.
How it is measured
Count engaged sessions and divide by all sessions in the same filter and period. The rule behind it decides the result: time, pages, events or a mix.
Tarsier reports a bounce figure per page and period. If you want engagement rate, define the rule first and compute it from the same session counts.
Worked example
A lighting retailer has 14,000 sessions in a month and 8,820 are engaged, a 63 percent rate. The blog runs at 78 percent and the paid-search landing page at 41 percent. The paid page is the problem.
They find the ad promises free shipping and the page never mentions it. After the copy change the page reaches 58 percent.
How it differs
Engagement rate is a percentage. An engaged session is the unit. Bounce rate is its complement under a matching rule. The rule matters more than the label.
Common errors
Treating the rate as a score. Comparing rates built from different rules. Using it on tiny samples. Skipping a split by device. Optimising the rate instead of the outcome.
In practice
Look at it by landing page and channel. Act only on segments with real volume, and fix mismatches between the promise and the page first.