Data Capture and Correctness

• Data validation is the process of checking if data satisfies certain criteria when data enters a computer system.
• Data validation ensure that data inputted meets the requirements for valid or acceptable data as defined by the problem.
• Since inputted data may come from many possible sources, that is why data validation and verification is used to ensure that data is correctly inputted within the narrow range of the program's operation.
• Types of Validation Checks:

  • Presence Check
  • Type Check
  • Existence Check
  • Length Check
  • Range Check
  • Format Check
  • Check Digit
  • Integrity Check
  • Lookup Check
  • Batch Header Check
• Presence check ensures that data is actually present and not missed out.
• Existence check identifies whether a certain value provided by the programmer is present in the input data.
• Format check ensures that the data inputted matches a previously determined pattern and that particular characters have particular values.
• Check digit is used to check the vaildity of code numbers by adding an extra digit at the end which is calculated from the digits of the original code.
• This is how a check digit diagram is drawn, where the check digit is 2 :

  A) Weight

  B) Digit

  C) Sum of Products

  D) Remainder

  
• When data is transcribed from one medium to another, there is always a danger that errors will be introduced. Hence, data verification is used to prevent such errors and ensure that data entered is what the user intends to input.
• Data verification aims to mitigate errors such as:

  • Transcription Errors
  • Transposition Errors
• Transcription errors occur when data is misinputted from the original source, while Transposition errors occur when data is misinputted in such a way that values are accidentally swapped around.
• Types of Data Verification Techniques:

  • Proof Reading
  • Visual Check
  • Double Entry
  • Check Digits
  • Batch totals
  • Control totals
  • Hash totals