Validation and verification
Two different checks on data entry, and the types of validation check.
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Learning objectives
What you need to be able to do
Teacher-mapped phrasing — check against the official Cambridge syllabus for exact wording.
- 18.2.1Distinguish between validation and verification and describe the main validation checks.
5 minute read
Validation and verification
These two are constantly confused, and the distinction is simple once stated precisely.
Validation
Validation is an automatic check by the computer that data entered is reasonable and sensible — that it could be right. It cannot tell whether the data is actually correct. The main checks:
- Range check — the value lies between limits, e.g. a month between 1 and 12.
- Type check — the data is the right type, e.g. only digits in an age field.
- Length check — the right number of characters, e.g. a password of at least 8.
- Presence check — a required field is not left blank.
- Format check — the data matches a pattern, e.g. a date as dd/mm/yyyy.
- Check digit — an extra digit calculated from the others, used on barcodes and ISBNs to detect mistyping.
- Lookup check — the value is one of a permitted list, e.g. a valid subject code.
Verification
Verification checks that data has been copied or entered accurately from the source. Two methods:
- Double entry — the data is entered twice and the computer compares the two versions, e.g. typing a new password twice.
- Visual (proofreading) — a human compares the entered data with the original document.
The distinction that earns marks
A date of birth of 01/01/1990 for someone born 02/02/1991 is valid — it passes every check — but it is wrong. Validation cannot catch this; only verification against the source can. So: validation asks "is this sensible?"; verification asks "is this what was on the form?"
Think of it like this
Validation is a bouncer checking you look old enough; verification is checking your ID against the guest list. The first rejects the obviously implausible, the second confirms you are actually who you claim.
Worked examples
Method, step by step
A student types their date of birth incorrectly but the system accepts it. Explain why validation did not detect the error, and state what would.
- 1Validation checks only whether the data is reasonable — a valid date in the correct format within an acceptable range.
- 2The mistyped date still satisfies all of these, so it is accepted as sensible.
- 3Only verification, comparing the entry against the original source document, can reveal that it is not the correct date.
The mistyped date was still sensible and correctly formatted, so it passed validation. Only verification — proofreading against the original form, or double entry — could detect that it does not match the source.
Common misconceptions
- Saying validation ensures data is correct. It only ensures data is reasonable — a plausible but wrong value passes easily.
- Listing "double entry" as a validation check. It is verification, because it compares two copies rather than testing reasonableness.
- Confusing a format check with a type check. Format is about the pattern (dd/mm/yyyy); type is about the kind of data (numeric, text).
In the exam
- If asked for a validation check, name the check **and** give an example rule for the specific field in the question — "range check: the mark must be between 0 and 100".
- Never offer a validation check as the answer to "how can you make sure the data matches the paper form" — that question requires verification.