Data  Verification is performed to ensure that the data entered exactly matches the original source.

There are two main methods of verification:

1. 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.

2. Proofreading data - this method involves someone checking the data entered against the original document. This is also time consuming and costly.

Validation
Validation is an automatic computer check to ensure that the data entered is sensible and reasonable.

Validation does not check the accuracy of data.

If a computer is programmed to accept numbers 1 to 10. It is a range check.

Types of validation

Check digit :  
The last one or two digits iused to check the other digits
Example : ISBN, VISA credit card, bar code readers  use check digits

Format check : 
Checks the data is in the right format : Phone numbers

Length check :
Google password needs to be minimum 8 characters

Lookup table :
Looks up acceptable values  (Gender, Months 1-12)

Presence check :
If data completed ? is @ mark in email ?

Range check :
Is the value falls within the specified range?  Number of over time hours worked for a day 0 - 3 hours

Spell check :
Looks up words in a dictionary    when word processing