2. Chapter 3 Data Control

3. Ensure the Accurate and Complete data is entering into the data processing system.

4. Sources of error Data Collection errors Enter wrong information onto the source documents. E.g.. Poor handwriting Data Preparation errors Transcription error Data on the source document are copied incorrectly. Data Input errors Typing error

5. Preventive Measure: Data Verification Data Validation

6. Data Verification Checking the accuracy of data has been copied from one medium to another. Usually takes place at the DATA PREPARATION or DATA INPUT stage.

7. Verification Process: It involves two operators to type the same set of data independently. First operator types in the data. Second operator re-enters all the data. A computer program compares both input. Alert the operator if Discrepancies occurs.

8. Data Validation Ensure data is valid and acceptable for data processing. Done by validation program.

9. Data Validation Methods Presence check Range check Data type check Consistency check Control total(batch total) Hash total Check digit

10. Data Validation Method Presence Check Ensure the data are present. Range Check Ensure data lie within a certain range. Data type Check Ensure data type is correct.

11. Data Validation Check Digit is an extra digit appended to a code consisting of a series of numbers or characters. Detect errors arising from transcription.

12. Modulo 11 Check 53622 / 11 = 4874 … 8 Remainder = 8 which equals to the check digit. The input data is correct. 53622 (8) Check digit

13. Modulo 11 Check 53627 / 11 = 4875 … 2 Remainder = 2 which NOT equals to the check digit(8).The input data is INCORRECT. Check digit 53622 (8) Original 53627(8) Input

14. Modulo 11 Check 526328 / 11 = 47848 … 0 Remainder = 0 which equals to the check digit(0).The input data is also considered as CORRECT but in fact it is incorrect. Check digit 536228 (0) Original 526328(0) Input

15. Weighted modulo 11 check A weight is given to each digit. 5 3 6 2 2 X 3 = 6 X 2 = 4 X 4 = 24 X 5 = 15 X 6 = 30 79 11 = 7, remainder=2 Subtract the remainder from 11 to get the check digit, 11 – 2 = 9 (9)

16. Weighted modulo 11 check for Account Number A weight is given to each digit. 5 3 6 2 2 X 3 = 6 X 2 = 4 X 4 = 24 X 5 = 15 X 6 = 30 88 11 = 8, remainder=0 So, the account number is valid. (9) X 1 = 9

17. Weighted modulo 11 check for ID card number A weight is given to each digit. Z 4 5 3 7 1 2 X 3 = 3 X 2 = 4 X 4 = 28 X 5 = 15 X 6 = 30 (3) X 7 = 28 X 8 = 208 A = 1 B = 2 C = 3. Z = 26 308 11 28 …8…8 Check digit = 11 – 8 = 3

18. Differences between Data Validation and Data Verification Data VerificationData Validation Checking data that have been copied from one medium to another. Check validity of data before they are processed. Include Invalid data after data verification. Exclude Invalid data after data validation. Takes place at data preparation stage. Takes place at data input stage (prior to processing).