1. Objectives
TO UNDERSTAND THAT CAPTURING DATA IS VALIDATED AND VERIFIED TO CHECK THAT IT IS REASONABLE AND CORRECT

2. Data types Alpha numeric – text and numbers
Numeric – integer, currency, percentage etc
Date/Time – DD/MM/YYYY
Limited choice – drop down lists, radio buttons, tick list
Object – picture
Logical/Boolean – e.g. Yes/no, true/false
Coding – Male, Female e.g. M or F

3. validation
Automatic checks performed by the computer to test whether the data is reasonable and sensible and in a valid format.
Seven validation tests:
Presence Check – ensures a field has not been left blank
Length Check – value is not longer than particular number e.g. 11 digits for mobile phone number
Range Check – Value is between two values e.g. between 1 and 10
Format Check – e.g. post code BB22 2TZ
Data Type Check – e.g. currency, text, number etc
Check Digit – Calculation to ensure code is a valid code
Parity Check

4. Check digit example Our example barcode data is 69277198116.
Add the digits in the odd-numbered positions (first, third, fifth, etc.) together and multiply the total by three.
=31   31x3=93
Add the digits in the even-numbered positions (second, fourth, sixth, etc.).
=26
Add the two results together.
93+26=119
Now what single digit number makes the total a multiple of 10? That’s the check digit.
= 120
1 is the check digit for The full UPC number is now

5. Check digit example Our example barcode data is 65747565839.
Add the digits in the odd-numbered positions (first, third, fifth, etc.) together and multiply the total by three.
=43   43x3=129
Add the digits in the even-numbered positions (second, fourth, sixth, etc.).
=22
Add the two results together.
129+22=151
Now what single digit number makes the total a multiple of 10? That’s the check digit.
= 160
9 is the check digit for The full UPC (Universal Product Code) number is now

6. verification
Used to find mistakes in the data by using checks to see if the data that has been typed in is consistent with the data on the source document or with the original after communication.
Two verification tests:
Visual Checks - Proofread
Double-entry or Double Keying enter twice

9. Parity check
Sometimes when data is being transferred electronically from one place to another it can become corrupted.
A parity check is used to make sure that data has not been corrupted during transmission.
Data is transmitted as a binary pattern of 0s and 1s.
A parity check involves adding an extra 0 or 1, called a parity bit, to the binary pattern so that the total number of 1s in the pattern is either an even number, this is called even parity, or an odd number, this is called odd parity.

10. In even parity the parity bit is set to either 0 or 1 so that the total number of 1s adds up to an even number.
In this example there are four 1s so the value 0 is needed in the parity bit to keep the number of 1s even.

11. In odd parity the parity bit is set to either 0 or 1 so that the total number of 1s adds up to an odd number.
In this example there are two 1s so the value 1 is needed in the parity bit to make the number of 1s odd.

12. Coding data
When data is input using a manual input device such as a keyboard, errors often occur due to values being entered incorrectly.
A common mistake is to swap two letters or digits around; this is called a transposition error.
One method that can be used to cut down on errors like this is to use coded values for data.
Suppose that a field could contain one of three possible values; small, medium or large. Instead of typing in the full word each time we could instead type S, M or L.

13. The advantages of coding values are:
Fewer key presses are needed when entering a value in the field so there is less chance of the wrong keys being pressed;
Time is saved when entering data because there is less to type in each time;
Database packages allow automatic validation checks to be set up to make sure that only the allowed codes have been input in a field.