In short: Cost per interaction expresses the price of one chosen user response, such as engagement with an advertisement. Without a precise interaction definition and connection to business results, it is only an auxiliary metric.
How I use cost per interaction in practice
I use it only once it is clear who collects the data and who acts on it. First I verify the event in the browser and source system, then its transfer to the report and finally its business meaning. I document differences between platforms instead of forcing them into alignment.
What to watch
The tool is not a source of truth by itself. I need to know collection limits and correction options. Without checking duplicates and missing events, a precise calculation may rest on faulty input.
Questions for decisions
- Exactly how do we calculate the value and from which source?
- Which decision changes when the number rises or falls?
- What can distort or duplicate measurement?
- What do we compare the value with so it has business meaning?