Before trusting an analysis, inspect whether the dataset means what you think it means. Initial inspection examines structure, values, types, missingness, and distributions, while keeping business and data teams aligned. section 2.3
Check whether identifiers represent customers
Counting distinct customer_id and customer_unique_id values, then grouping one by the other, can reveal that one customer has multiple records. In the displayed results, counts range from 1 to 17, so treating every row as a separate customer would be unsafe.
