• Check the aggregation thresholds for the event tables in the Schema explorer
• Run the report multiple times and look for a variance in the results
• Use the Append aggregation threshold columns option in the Query editor
• NULL values don’t occur naturally within reports unless the query is invalid.

The correct answer is: Use the Append aggregation threshold columns option in the Query editor

Explanation: To determine whether NULL values in your AMC report are the result of aggregation thresholds or a natural occurrence in the data, use the Append aggregation threshold columns option in the Query editor.

Enabling this feature adds columns to your query output that indicate when a value is hidden or set to NULL to meet privacy requirements (aggregation thresholds). This distinction lets you identify whether NULLs are due to privacy rules (insufficient data to meet the threshold) or because the data is naturally missing.

Reference content: From Amazon’s official documentation – Aggregation Thresholds in AMC

“If your workflow is expected to contain NULL values, the best way to evaluate if a value is truly missing, or is being set to NULL for privacy reasons is to use the Append aggregation threshold columns option in the Query Editor. … These columns clarify if NULLs come from aggregation threshold enforcement or from non-populated data.”