4.1. 3 Validation and Verification

1. How data errors occur The purpose and types of Validation 4.1.3 Validation and Verification

2. Starter: QuestionCome up with a list of problems that may occur using inaccurate data? (5 mins)

3. Starter: Problems with inaccurate data • Incorrect decisions being made resulting in loss of money • Having to spend time sorting out mistakes • Loss of goodwill • Loss of trust • Prosecution under the DPA Act 1998 for not keeping personal data accurate. It is essential that techniques are built into any data entry method so that errors can be reduced, or eliminated.

4. Main: Where data errors can occur during… • Transcription • Input • Processing • Transmission Place these areas into a data cycle diagram

5. Main: Transcription Errors Avoiding Transcription Errors Avoid keyboard Accurate Automation Validation checks Transcription is when data is keyed in (transcribed) The process of copying data from a source document such as an order form or an application form. Errors: • Mistakes that humans make when either keying in data of filling in forms such as optical mark forms. • Often occuring through carelessness and not picked up through proof reading

6. Main: Input Errors Avoiding input errors Keep human involvement to a minimum and use direct methods of data capture such as MICR, ICR, bar coding, etc. Bar code readers in supermarkets make a beep that tells the operator that an item has been scanned correctly. If it does not beep the person can scan again or manually enter the bar code. • Input data, even though verified (checked against the source document) and validated, can still be incorrect. Examples • Human involvement at the data collection or input stage • Keyboarding • OMR or MICR e.g. a form may not be read by the reader because it is not marked correctly. If the system tried to guess what the mark should be this would introduce incorrect data, instead the system should reject the form.

7. Main: Processing Errors Problems with hardware and software Examples • Use of the wrong version of a data file for processing data rather than the latest version e.g. you could use an older version of a spreadsheet by mistake. • Incorrect formulas in spreadsheet that were not detected and corrected during the testing, means that incorrect processes are being performed, leading to wrong information being ouput. • Damage by viruses (viruses are able to delete data or render if unreadable). • Equipment malfunction – hard disks break down occasionally. This can cause loss of data, so it is important to back up files.

8. Main: Transmission Errors When data is passed through a communication medium (wireless, optic fibre, telephone line), it is important that the data is not corrupted in any way and if it is, it is important that this is detected and the data retransmitted. • The checking of data after it has passed along a communication line is performed using a parity check. Parity check = the computer adds up the number of bits in one byte and if the parity is different to the parity settings, the computer will report an error. • The problem with parity checks is that if more than one error occurs and the errors compensate for each other, parity can still appear to be correct. ASCII = American Standard Code for Information Exchange

9. Exam questions… (5 mins) • There are a number of ways in which data errors can occur. By giving an example in each case, describe how errors can occur during: • Input (2) • Transcription (2) • Processing (2) • Transmission (2) 2. If inaccurate data is processed, it can have a number of different consequences. Describe three distinctly different consequences of processing data that is incorrect. (6 marks)

10. Main: Complete (5 mins)Complete the spider diagram to match up the data errors to where they occur

11. Main: The Purpose and types of Validation

12. Main: Question ( 5 mins)What is Validation?

13. Main: ValidationValidation is a check performed by a computer program during data entryValidation is the process of making sure that the data is sensibleIt does not check the accuracy of data For example, a secondary school student is likely to be aged between 11 and 16. The computer can be programmed only to accept numbers between 11 and 16. This is a range check. However, this does not guarantee that the number typed in is correct. For example, a student's age might be 14, but if 11 is entered it will be valid but incorrect.

14. Main: Validation Checks • There are a number of different validation techniques that can be used: • Type check • Presence check • Range check • Pre defined value • Format check • Check digit. Match these to how they work (5 mins) http://www.bbc.co.uk/schools/gcsebitesize/ict/databases/3datavalidation_act.shtml

15. Main: Validation Techniques Add an example for each Check (5 mins)

16. Main: Validation Techniques • Type check • Check data is a given type • e.g. Number, Date or Time • Presence check • Check that field is not empty • i.e. user must enter something • Range check • Check that value is within a pre-defined range • e.g. age for driving licence is 17 – 70 • Pre defined value • Check that entry is one of a pre-defined list of possible entries • e.g. a current customer • Format check • Check the data is of a specified format • e.g. NI Number is XX 99 99 99 X • Check digit • An extra digit calculated on a number used as a self checking device • e.g. account no or reference number

17. Main: Before Validation Errors The most common errors during data entry are: Transcription Errors – errors made when typing data in using a document as the source of data. Transposition Errors - Errors made when characters are swapped around so they are in the wrong order

18. Main: Transciption Errors Transcription errors involves transferring data to the computer. Human operators who key in the data are faced with a number of problems Speech Unusual words spoken Poor handwriting Misinterpretation Typing mistakes

19. Main: Transposition Errors • Transposition errors are easy to make when typing at high speed and involves acidentlasawpingaronud of chraacters LOL • It has been estimated that around 70% of keyboarding errors are transposition • Examples • Fro instead of For • 100065 instead of 100056

20. Main: Memory Activity Think of a way to remember these as they are very similar Transcription & Transposition

21. Main: Practical Activity Using the worksheet provided complete the activity: Validating cells and creating Messages

22. Exam questions… (5 mins) Think about the types of mistakes you make when typing information into a computer. Write a list of three different mistakes you can make. (3 Marks) A computer manager says ‘data can be valid yet be incorrect’. By giving one suitable example, explain what this statement means. (3 marks)

23. Plenary: Quiz (5 mins) Quiz

24. Plenary: Quiz Validation. Format check. Range check. Presence check. Check digit. Length check. 21st June 2004. Validation can check that the data is correct. Quiz