UA Ledger · Measurement Lab · draft for review

Reconcile two attributed-install lists without counting their overlap twice

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First obtain an authorised matching rule that makes the two populations comparable. Count the records in each list and the records appearing in both. Add the two list sizes and subtract the shared count once. The overlap must be no larger than either input list. Do not manufacture a device-level match where privacy restrictions or different identifiers prevent one.

Calculated outputs

Assumption sensitivity

Only overlap varies; all other inputs are held constant. This is not a probability range.

Equations

• Distinct union: a+b-overlap
• Overlap share of summed claims %: 100*overlap/(a+b)

Additional constraints: (a+b>0) && (overlap<=Math.min(a,b)). The field minimums also apply.

Limits

The worksheet assumes exact, permitted matching. Probabilistic matching, re-installs and divergent conversion windows can invalidate that assumption and must be documented before using the union as an operational total.

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