Data Verification and Validation

• Data verification
  It is a method used to eliminate transcription (Typing data into a computer from a data capture) error.
• Methods of Verification
  
  • Proof Reading
    A visual check by eye that no errors have been made.This is sometimes done by printing out data that has been input, and sending it back to the source of the data to check. For example, printed proofs of the pages of a book may be sent back to the author for checking.
    
  • Double Keying the data
    This is a check to see if data has been keyed in correctly. The data is keyed in twice, and the computer will only accept the data for processing if the two versions are identical.
    
    
• Data Validation
  

  A validation check is an automatic check made by a computer to ensure that any data entered into the computer is sensible. A validation check does not make sure that data has been entered correctly. It only ensures that the data is sensible. For this reason validation checks are not usually as effective as verification checks. They can however be carried out automatically by a computer and therefore require less work by computer operators making them cheaper to use.
  

• Methods of Validation
  

  There are many different methods of validation. The most appropriate method(s) to use will depend upon what data is being entered. The most common methods are listed here.
  

  • Presence Check
    Checks that data has been entered into a field and that it has not been left blank. e.g. check that a surname is always entered into each record in a database of addresses.
    
  • Type Check
    Checks that an entered value is of a particular type. e.g. check that age is numeric.
    
  • Length Check
    Checks than an entered value e.g. surname is no longer than a particular number of characters.
    
  • Range Check
    Checks that an entered value falls within a particular range. For example the age of a person should be in the range 0 to 130 years.
    
  • Format Check
    Checks that an entered value has a particular format. e.g. a new-style car registration number should consist of a letter followed by 1 to 3 numbers followed by 3 letters.
    
  • Check Digit
    A check digit is a digit attached to the end of a string of digits. It is calculated from the other digits and used to help ensure that the whole string is inputted correctly. The most common check digit is the one on the end of the ISBN
    
  • Parity Check
    Used in data communications to ensure that data is not corrupted when it is sent down a transmission medium such as a telephone line.