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madhuraj87
Level 2
Nov 19, 2025 4:19 PM UTC
Question

Does the Target Sample Size Calculator apply to CJA reporting?

I often use the calculator to decide how long to run an A/B test. Up until recently we've just used Target as the reporting source, but have recently enabled CJA which we're beginning to use.

 

When using CJA to report out on Target activities (via the Experimentation Panel), I've noticed that the lift and confidence can take much longer to calculate than it would with the same page/page traffic in Target. Is this because we're applying the success metrics after the fact, rather than defining them within the VEC? And does that mean we should be using another calculator to determine test duration when using CJA as the reporting source?

 

Thanks in advance!

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    3 replies

    Adobe Employee
    SarthakBhAdobe Employee
    Adobe Employee
    Jan 27, 2026 3:40 AM UTC

    Target and CJA use different algorithms for statistics; Target uses a classical/Welch t‑test–based model.  Because Target and CJA are using different statistical models, they will not agree on duration/sample size. 

    You can refer to doc https://experienceleague.adobe.com/en/docs/analytics-platform/using/cja-components/cja-calcmetrics/cm-adv-functions#lift on how lift, confidence and other metrics are calculated in CJA

     

    Thank you! 

    Sarthak Bhatt | Senior Product Consultant | Customer Experience | Adobe  

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      Perrin_Ennen
      Community Advisor
      Perrin_EnnenCommunity Advisor
      Community Advisor
      Jan 28, 2026 7:08 AM UTC

      Hi ​@madhuraj87,

      the Adobe Target Sample Size Calculator still applies when using CJA for reporting, because the underlying experiment design and assumptions do not change. However, CJA metrics are evaluated after exposure and require additional processing (ingestion, stitching, attribution), which can delay lift and confidence stabilization compared to native Target reporting. When using CJA as the primary reporting source, it’s best to plan for longer runtimes or add a buffer to the calculated duration, especially if success metrics are not defined in the Target activity itself.

       

      Hope this helps.

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        madhuraj87Author
        Level 2
        Jan 28, 2026 3:32 PM UTC

        This makes sense - thank you!

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