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
Range
Presence
Check digit
Length
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
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
Type of check that
could be used
Activity
Check at least 2 other examples for each of the
following types of validation check:
• Presence check
• Length check
• Check digit
• Type check