Control group & lift

The idea, simply

Imagine 100 clients are due. We message 90 of them and deliberately don’t message the other 10. Three weeks later, 45% of the messaged group has booked, and 30% of the unmessaged group has booked anyway. The messages brought back an extra 15 percentage points — that’s the lift.

Without the comparison group, you’d credit the messages for everyone who came back, including people who were coming anyway.

How clients are picked

• By default 10% of due clients are held back (set 0–50% in Settings → Messages & reminders → Comparison group).
• The pick is random but fixed for each visit cycle — the same client may be messaged next time.
• Held-back clients get no comeback from any path, including Send now.
• Reminders, waitlist offers and replies are not affected.

How lift is measured

1. 1

   Every rebook comeback planned in the period counts

   Including ones later skipped. Win-backs aren’t included.

2. 2

   “Came back” means

   A confirmed or completed booking made between planning and 21 days after the due date.

3. 3

   Lift

   Return rate of the messaged group minus return rate of the held-back group, in percentage points.

• Lift is shown only once both groups have at least 20 due clients.
• The Comebacks page also shows a likely range, and labels the result clear, early (fewer than 100 in the smaller group) or unclear (the range includes zero).
• Extra visits = the lift × the number of messaged clients.
• “Is it working?” covers the last 90 days and is the same calculation on the Comebacks page and in Results, so the two can never disagree.