1. Review of Data Capture

2. Input Devices What input devices are suitable for data entry? Keyboard Voice Bar Code MICR OMR Smart Cards / Magnetic Stripe cards Key to Disk systems Scanners / OCR

3. Scanners can be used to read typed documents OCR (Optical Character Recognition) software can then be used to interpret the text and export it to a word processor or data file for editing Very powerful OCR software can also convert neat handwriting Scanners are also used to input large volumes of data on pre-printed forms such as credit card payments where data is in a specific place

4. Summary Different input devices are suitable in different situations Speed Accuracy Cost Input devices that capture data directly (e.g. MICR) reduce errors However much data is still keyed directly into the system

5. Validation & Verification

6. Preventing errors Validation & verification are used to prevent errors!

7. What errors????? The customer could make a mistake The person entering the data could make a transcription error The form may be lost The form may be entered twice by mistake The data could be lost due to network failure

8. Validation Validation is the process of making sure that the data is sensible Validation is performed by the computer Presence Check Format Check Range Check File lookup check Check digit

9. Check Digit 1 Code numbers such as a customer no., employee no. or product no. are often lengthy and prone to error. One way of preventing these errors is to add an extra digit to the end of a code number which has been calculated from the digits of the code number. In this way the code number with its extra check digit is self-checking. Best-known method of calculating check digits is the modulus-11 system, which traps over 99% of all errors.

10. Check Digit 2 1. Each digit of the code number is assigned a ‘weight’. The right hand (least significant) digit is given a weight of 2, the next digit to the left 3 and so on. 2. Each digit is multiplied by its weight and the products added together. 3. The sum of the products is divided by 11 and the remainder obtained. 4. The remainder is subtracted from 11 to give the check digit. The two exceptions are: a) If remainder is 0, check digit is 0, not 11 b) If remainder is 1, check digit is X, not 10

11. Check Digit 3 To calculate the check digit for the number 1587: Original code number1 5 8 7 Weights5 4 3 2 Multiply digit by its weight5 20 24 14 Add products together5 + 20 + 24 + 14 = 63 Divide by 115 remainder 8 Sub remainder from 1111 - 8 =3 Check digit = 3. Complete code number is 15873.

12. Accuracy & Validity Valid data is not always accurate Surveying people in town at 10am on a Thursday will give valid data, but not an accurate representation of everyone’s views Valid data is not always correct 15 is a valid age But is not my age!

13. Verification Verification is the process of making sure that the data correct Verification cannot be performed by the computer Usually done by double entry Often done by an 3 rd party

14. Parity Data errors can be introduced in transmission Even parity – there is a even number of 1’s in the data Odd parity– there is a odd number of 1’s in the data 11010001101010100111110011101010