ICT
Data validation and verification
Validation and verification are two ways to check that the entered into a computer is correct. Datadata: information without context, eg a list of students with numbers beside their names is data, when it's made clear that those numbers represent their placing in a 100 metre race, the data becomes information entered incorrectly is of little use.
Validation is an automatic computer check to ensure that the data entered is sensible and reasonable. It does not check the accuracy of data.
For example, a secondary school student is likely to be aged between 11 and 16. The computer can be programmed only to accept numbers between 11 and 16. This is a range check.
However, this does not guarantee that the number typed in is correct. For example, a student's age might be 14, but if 11 is entered it will be valid but incorrect.
There are a number of validation types that can be used to check the data that is being entered.
| Validation type | How it works | Example usage |
|---|---|---|
| Check digit | the last one or two digits in a code are used to check the other digits are correct | bar code readers in supermarkets use check digits |
| Format check | checks the data is in the right format | a National Insurance number is in the form LL 99 99 99 L where L is any letter and 9 is any number |
| Length check | checks the data isn't too short or too long | a password which needs to be six letters long |
| Lookup table | looks up acceptable values in a table | there are only seven possible days of the week |
| Presence check | checks that data has been entered into a fieldfield: a smaller piece of data in larger collection, eg name in an electronic address book, where name is a field | in most databasesdatabase: a structured collection of records or data stored in a computer system a key fieldkey field: a unique identifier for a database record or table entry cannot be left blank |
| Range check | checks that a value falls within the specified range | number of hours worked must be less than 50 and more than 0 |
| Spell check | looks up words in a dictionary | when word processing |
Verification is performed to ensure that the data entered exactly matches the original source.
There are two main methods of verification:
Double entry - entering the data twice and comparing the two copies. This effectively doubles the workload, and as most people are paid by the hour, it costs more too.
Proofreading data - this method involves someone checking the data entered against the original document. This is also time consuming and costly.
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