Email Matched Market Testing

Definition

Email matched market testing compares the performance of different campaign strategies by applying them to similar but separate subscriber segments. Unlike classic A/B testing where random halves of the same segment receive different variants, matched market testing uses structurally similar groups — such as subscribers acquired through the same channel in different time periods, or subscribers with similar demographic profiles in different regions. This approach is useful when A/B testing is impractical due to segment size, when testing fundamental strategy differences rather than content variations, or when interaction effects between test variants are a concern.

When to Use

• Segment size is too small for statistically significant A/B test results
• Testing fundamentally different strategies that would interact if applied to the same segment
• Evaluating the impact of programme changes against a control group that should not receive the change
• Measuring long-term effects that require sustained exposure to a strategy rather than single-send testing

Limitations

• Matched groups are never perfectly equivalent, introducing potential confounding variables
• Requires careful selection of matching criteria and statistical controls
• Smaller differences between variants require larger group sizes to detect reliably
• Results may not generalise beyond the specific matched groups tested

Best Practices

• Document the matching criteria and rationale before testing to avoid post-hoc justification
• Use multiple matched pairs to increase confidence in results
• Combine matched market testing with single-send A/B tests where possible for cross-validation
• Apply statistical controls for known differences between matched groups in the analysis
• Consider matched market testing as complementary to rather than a replacement for randomised testing