3.2 Data Checking

Overview

Demonstrate knowledge and understanding of data verification and validation techniques.

Identify the most suitable data validation techniques for given situations from type, range, presence, check digit and length.

Verification

A way of checking that data has been entered into a computer system correctly or

transferred correctly from one medium to another.

Verification methods

• Entering the information twice. The first version is compared with the second version and if the two do not match then an error is reported.

• Proof reading the entered data.

Validation

A method of ensuring that data entered into the system is reasonable and correct.

Examples include:Type

RangePresence

Check digitLength

Type

A validation check that makes sure that the characters entered are of the right type.

E.g.• They are all letters• They are all numbers• The first is a letter and the rest numbers

etc.

Range

A validation check that ensures that the data entered is between two defined limits. An

upper limit and a lower limit.E.g.A child at primary school is between 4 and

11.A car driver is between 17 and 80.A car does not need an MOT between 0 and

4 years of age.

Presence

A validation check that makes sure that the data has actually been entered and exists. There is

no missing data.

Check digit• A character placed at the end of a list of

numbers that ensures that the list of numbers has been entered correctly.

• This end character (check digit) is produced using a mathematical formula on the list of enter numbers.

• If, when the numbers are entered and the calculation performed, it does not match the check digit then an error is reported.

Check digit example

Length

A validation check to see if the characters entered are of a certain length.

E.g. • 4 characters • 8 characters• 5 characters

Discussion

Application Type of check that could be used

Making sure all examination marks are entered

Making sure that examination marks are between 0 and 100

Ensuring the number under a bar code has been typed in correctly

Checking a postcode is valid

Checking that a works number has been entered as numbers only

Activity

Check at least 2 other examples for each of the following types of validation check:

• Presence check• Length check• Check digit• Type check