Practice prompt · Q:statistics-estimation-and-uncertainty/unit-variable-001

Identify the unit after a payment join

Diagnose a grain error when several payment records appear for one invoice.

Updated Aug 7, 2026 Review due Nov 7, 2026

Practice

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Choose a response, then check the answer and explanation.

Assessment-specific hypothetical: Juniper joins invoice headers to payment applications. One invoice paid in three installments now appears on three rows. The intended analysis gives each invoice equal weight when summarizing days from issue through final settlement. Which response preserves the declared unit?

The item checks whether the learner controls the case before the calculation. The variable remains days to final settlement; the joined row is not automatically the intended unit.

Choose the best answer. a Treat each joined row as an invoice because every row contains an invoice ID. b Collapse or reconcile payment rows to one unique invoice record, then compute the final-settlement variable once per invoice. c Average the invoice IDs first, then use that average as the row key. d Keep all payment rows and divide the final mean by the number of installments.

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Answer: b

Choice b. Re-establish one row per qualifying invoice, verify the unique key, and derive days to final settlement from the reconciled payment history.