1. 3.2 Data Checking

2. 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.

3. Verification
A way of checking that data has been entered into a computer system correctly or transferred correctly from one medium to another.

4. 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.

5. Validation
A method of ensuring that data entered into the system is reasonable and correct. Examples include: Type Range Presence Check digit Length

6. 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.

7. 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.

8. Presence
A validation check that makes sure that the data has actually been entered and exists. There is no missing data.

9. 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.

10. Check digit example

11. Length
A validation check to see if the characters entered are of a certain length.
E.g.
4 characters
8 characters
5 characters

12. Discussion Application Making sure all examination marks are entered
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

13. Activity
Check at least 2 other examples for each of the following types of validation check:
Presence check
Length check
Check digit
Type check