Missing Data and Outliers | Dataford Interview Questions

Describe how you would handle missing data or outliers in a large financial dataset.

For this SQL exercise, classify each transaction without silently replacing missing or unusual amounts. Treat non-null amounts outside the 1.5 IQR range as outliers, using the overall non-null transaction distribution.

Output

One row per transaction with transaction_id, account_type, amount, and data_quality_status
Include missing amounts, outliers, and valid amounts
Sort by transaction_id ascending

Schema

accounts

Column	Type	Description
account_idPK	INT	Unique financial account identifier
account_type	VARCHAR(50)	Classification of the financial account

financial_transactions

Column	Type	Description
transaction_idPK	INT	Unique transaction identifier
account_id	INT	Related account identifier
transaction_date	DATE	Date on which the transaction occurred
amount	NUMERIC(12,2)	Transaction amount, which may be missing

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