How many customers you need before judging a campaign
Datarithms gives no verdict on a campaign until it has at least 30 paying customers in the period. Below that, one customer more or less moves the cost per customer so much that a ranking mostly reflects luck. The campaign is shown as "too few to tell", with its counts.
Why do small numbers swing so much?
With 4 customers, one extra customer is a 25% change. With 40 customers, one extra is a 2.5% change. The cost per customer of a small campaign can halve or double from one week to the next without anything real changing.
| Campaign | Spend | Paying customers | Cost per customer | With one more customer | With one fewer |
|---|---|---|---|---|---|
| Job title targeting | $1,960 | 4 | $490 | $392 | $653 |
| Lookalike, sign-ups | $5,570 | 48 | $116 | $114 | $119 |
The small campaign's cost moves by up to $163 on a single customer. The large one moves by $3.
Why 30 and not another number?
30 is Datarithms' own rule, not a statistical law. We chose it because at 30 customers one customer more or less moves cost per customer by only about 3%, and because it is easy to remember and check. A campaign with 31 customers is not proven good; it has simply earned a position in the table.
What should you do with a campaign below 30?
- Decide in advance how much you are willing to spend before judging it.
- Let it run long enough to collect 30 paying customers, or stop it for reasons other than its cost per customer.
- Do not compare its cost per customer with established campaigns yet.
Related pages
- How to calculate cost per paying customerSpend divided by customers who paid and stayed. How to count both sides honestly.
- How to run a weekly ad budget reviewA 30-minute weekly routine: read the table, decide changes, re-check after 28 days.
- LinkedIn Ads and paying customersLinkedIn leads and conversions, lead forms, long sales cycles, and the export we need.
- How it worksThe matching rules behind the weekly table: last ad click within 90 days, refunds within 14 days excluded, no verdict under 30 paying customers.
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