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Activity per Period

Overview​

An Activity per Period metric measures how frequently a user performs a goal action across a configurable time window — for example, sessions per week or orders per month.

Unlike a simple Goal Count, which sums all events per user, Activity per Period normalises activity into a rate per period, making it easier to compare user engagement over time and across cohorts of different exposure lengths.

You can configure:

  • the goal event to track
  • the period length (e.g. day, week, month)
  • whether the period starts:
    • from the user's first exposure to the experiment, or
    • from the user's first occurrence of the goal event

Examples​

context.track("session_start", {
  source: "homepage",
  device: "mobile"
});

Imagine you want to measure average sessions per week per user during your experiment.

You can create a Sessions per Week metric by:

  • Selecting the session_start goal
  • Setting the Period to 7 days
  • Choosing whether periods start from the user's first exposure or first session

The metric then computes, for each user, the number of goal events per period, and aggregates the result across the experiment population.

More examples

  • Orders per Month: Average number of purchases per user per 30-day period.

  • Articles Read per Week: Average number of articles read per user, per 7-day period.

  • Active Days per Week: Average number of distinct days a user was active in a 7-day window.

Good to know​

  • Useful when you care about frequency of an action rather than total volume or simple conversion.
  • More robust than Goal Count when users have different exposure lengths — the per-period normalisation makes long-tenured and short-tenured users directly comparable.
  • Filters on the goal event apply before the per-period rollup (for example: purchases per week restricted to a specific category).
  • Changing the period length alters the meaning of the metric and will require a new version.
  • Ideal for experiments aimed at engagement, habit formation, or retention frequency — onboarding flows, notifications, recommendation systems, or loyalty mechanics.