Data Integrity — common mistakes

Examiners frequently ask for the difference between validation and verification. Remember: Validation is an automated check for sensible data (e.g., is the age between 0-120?). Verification is a check for transcription errors (e.g., did you type what you meant to type?). Be specific in your answers; 'a check' is too vague. Name the type of check, e.g., 'a range check' or 'double entry verification'.

Absolutely. Validation only checks if data is reasonable, not if it's factually correct. For example, if you are entering a customer's age and their true age is 34, but you accidentally type 43, a range check (e.g., 18-99) would pass. The data is valid, but it is not correct.

A check digit is a type of validation. It's an automated, mathematical check performed by the system on a single piece of data (the number) to see if it's internally consistent and likely to be valid. It doesn't involve comparing the data to an original source, which is the hallmark of verification.

A type check ensures the data is of the correct data type (e.g., INTEGER, STRING, BOOLEAN). A format check is more specific; it checks that a string follows a particular pattern (e.g., a postcode like 'SW1A 0AA' follows the pattern LLNA NAA). A postcode passes a string type check, but might fail a more specific format check.

Double entry is generally more reliable because the comparison is done automatically by the computer, which doesn't make mistakes or lose concentration. A visual check relies on human proofreading, which is prone to error, especially when dealing with large amounts of data or long strings of numbers.