Split Testing

Measure lift by comparing users who see your ads with a control group that doesn't.

Split testing measures incremental impact at the user level. Your audience is divided into two groups:

  • Treatment group: sees your ads.
  • Control group: is held out and doesn't see your ads.

Both groups are otherwise alike. So any difference in conversions between them is the lift your ads caused.

How a split test works

  1. Assign users: Users are randomly split into treatment and control groups.
  2. Run the test: Ads are shown only to the treatment group for the test period.
  3. Normalize the control: The control group is adjusted to match the size of the treatment group, so results compare fairly.
  4. Measure lift: Conversions in both groups are compared to calculate incremental impact.
  5. Check significance: Results are tested to confirm the lift is real and not due to chance.

Learn more

ArticleWhat it covers
Statistical SignificanceHow to tell if your test results are reliable
Treatment / Control AssignmentHow users are split into test and holdout groups
Understanding Normalised ControlHow the control group is scaled for a fair comparison

When to use split testing

  • You can target and hold out audiences at the user level.
  • You want a fast, direct read on a channel, campaign, or audience.
  • You need clean results to calibrate your Marketing Mix Model.

When user-level tracking is limited, Geo-Testing measures lift through regional differences instead.


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