Incrementality testing and experiment split testing
True marketing maturity requires testing incremental lift. Here is how to construct A/B split experiments and measure true causal conversion impact.
The science of incrementality in paid search#
Correlational performance metrics can be misleading. Incrementality testing isolates causal lift by splitting incoming search auctions between a control campaign and an experimental trial.
As explained in Microsoft Experiments Documentation, 2026, traffic is randomly assigned at the user or cookie level, preventing auction overlap.
Configuring 50/50 split experiments#
When creating an experiment, allocate a 50% budget and traffic split to ensure balanced statistical power.
Test a single isolated variable (e.g., Target CPA vs Target ROAS, or New Landing Page vs Control) as detailed in Microsoft Experiments API Guide, 2026.
Never change multiple variables simultaneously in an experiment; isolated variables guarantee unambiguous attribution of results.
Evaluating statistical significance thresholds#
Run experiments until achieving at least 95% statistical confidence, requiring a minimum of 100 conversions per branch over a 30 to 45-day testing window.
Graduating winning experiments into production#
When an experiment proves statistically superior, click 'Apply' to merge trial changes directly into the original base campaign seamlessly.
Explore our Microsoft Ads Hub for experiment design templates.
High-impact experiment testing framework#
The table below outlines high-yield testing ideas for Microsoft Advertising experiments.
| Testing Category | Control Parameter | Trial Variation | Primary Success Metric |
|---|---|---|---|
| Bidding Strategy | Enhanced CPC (Manual) | Target CPA (Smart Bidding) | Cost Per Acquisition & Volume |
| Landing Page Design | Standard Long-Form Page | Interactive Assessment Page | Conversion Rate & Bounce Rate |
| URL Expansion (PMax) | URL Expansion OFF | URL Expansion ON | Incremental Revenue vs Waste |
| Broad Match Scale | Exact & Phrase Match Only | Broad Match + Target CPA | Incremental Conversion Lift |
Frequently asked questions#
What is an Experiment in Microsoft Advertising?
An Experiment is an A/B split testing tool that splits search auctions and budget between your original campaign and a modified trial version to measure performance differences.
Do experimental campaigns compete with the original campaign in the auction?
No, Microsoft randomly splits user auctions before entering the public marketplace, ensuring your control and trial campaigns never bid against each other.
How long should a Microsoft Ads experiment run?
Experiments should run for at least 30 to 60 days to collect enough conversion data for statistical significance.
What happens when I apply a winning experiment?
Clicking 'Apply' automatically updates your base campaign with the experimental settings while preserving historical campaign IDs and Quality Scores.
Can I run experiments on Shopping campaigns?
Yes, Microsoft Advertising supports experiments across standard Search and Shopping campaigns.
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