How Data Errors Occur
Problems with Inaccurate Data
- Errors in data can cause problems -> Incorrect decisions leading to a loss of money, goods being sent to the wrong address, loss of trust, spending time to sort out mistakes etc.
How Data Errors can Occur During Input, Transcription, Processing and Transmission
- TRANSCRIPTION -> Mistakes humans make and usually occur through carelessness and they're errors that occur during the keying in process -> Training and emphasising the importance can help to minmise these errors
- INPUT -> Input data can still remain incorrect and this can because of the human involvement -> Keyboarding can introduce a large number of errors during the input process and automated methods can too
- PROCESSING -> Programming error that isn't known about, use of wrong version of a file, incorrect formulas in spreadsheets, damage by viruses, equipment malfunction
- TRANSMISSION -> Parity checks check data after passed along a communication line (adds up no. of bits in one byte and if the parity contrasts to the parity setting it will report an error -> Communication devices contain a chip which deals with the parity checks -> If more than one error occurs and they compensate for each other, parity can still appear to be correct
The Purpose and Types of Validation
Validity and Correctness of Data
- Data has to comply to specific rules for it to be valid e.g. field requiring numbers won't allow letters
- If a name is mispelt it would still be accepted because it is in the correct form of data
Types of Error which can Occur During Data Entry
- TRANSCRIPTION ERRORS -> Where data is transferred from one medium to another -> Problems include: problems with understanding speech, a caler not spelling out complicated words or names, poor handwriting, misinterpretation + typing mistakes
- TRANSPOSITION ERRORS -> Easy to make when typing very fast and they are where characters are swapped around e.g. 'fro' instead of 'for'
The Purpose and Types of Validation Continued...
- Check performed by a computer program during data entry and it is the process that makes sure that data accepted is sensible and reasonable -> Validation checks
Validation Checks (Examples, not all are Included)
- DATE TYPE CHECKS - Check if the type of data being entered is the same type as the one which the field requires
- PRESENCE CHECKS - Checks if data has been entered into a specific field and if it hasn't then the data won't be processed
- LENGTH CHECKS - Checking if the data has the correct number of characters in it e.g. six-digit account number will be checked to ensure that it has six characters (no more + no less)
The Purpose and Types of Validation Continued...
Validation Checks - Check Digits
- They're added to important numbers like International Book Numbers
- They're then placed at the end of the block of numbers and they are utilised to check that the numbers have been entered correctly into the computer
Limitations of Error Checking
- Errors can still occur even if there are validation checks in place
- Somebody may think they know how to spell someone else's name when it may be spelt different to what they think it is
- Errors can be reduced -> Reduce the quantity of typed input, allow someone to type in their details, allow them to check their details to see if they are correct and ensure that lots of validation and verification methods are used
The Purpose of Verification
DEFINITION - CHECKING THAT THE DATA BEING ENTERED INTO THE ICT SYSTEM PERFECTLY MATCHES THE SOURCE OF THE DATA
Methods of Verification
- PROOF READING - This is where a user carefully reads what they have typed in and comparing it to what is actually on the data source for any mistakes/errors which can be easily corrected
- DOUBLE ENTRY OF DATA - This is where two people utilise identical data sources to enter details of it into the ICT system and the data will only be accepted if the two sets are exactly the same (Cost of data entry is double)
- SENDING BACK PRINTOUTS - This is where information is printed out and sent back to the person who supplied it in the first place to see if they can spot any mistakes/errors e.g. Booking holidays over the phone
The Purpose of Validation Continued...
Verifying and Validating Content
- During the development of multimedia products it's necessary to check the content or the arrangement of the content by checking accuracy, readability, spellchecking, grammar checking and checking all of the content is there etc.
Examples of Verification
- DOUBLE ENTRY OF DATA - Passwords are usually entered in twice and will only be accepted if both of them match (when creating passwords)
- PROOF READING - e.g. Pupil details being entered into a pupil database wil be checked, after they have been inputted, with information from a form to ensure that the information is the same
- SENDING BACK PRINTOUTS - e.g. When buying a CD using the Internet, you have to make your choices usually by adding your purchases to the shopping trolley -> After you have reached the checkout and paid for your purchases, you will receive a confirmation e-mail
The Purpose of Verification Continued...
Avoiding Human Error
- Keyboards need to be replaced by direct input methods
- Direct input methods improve the accuracy of input but can still produce errors e.g. Scanner used to read the marks on an optical form may read imperfections in the paper or card as marks