6.2 Data Integrity

# Data Integrity
- ensuring the consistency / accuracy of the data
## Validation
- checks that data is reasonable / sensible
- example e.g. checking data is the right number / type of characters
- It does not check that accurate data has been entered
### Range check
- Make sure it is after and before a specific date 
- e.g. check month is between 1 and 12
### Format check
- the registration number must be in the format (**Please combine the questions:** eg. letter-digit-digit-digit-letter-letter).
### Presence check
- Make sure the date of birth has been entered
### Length check
- **Please combine the questions:** the registration number must be 6 characters long.
### Type check
- **Please combine the questions:** the registration number must be alphanumeric(integer, date).
## Verification
- Manually compare the data entered with the original (document)
- It does not check if the original data is accurate
#### Double entry
- Enter the data twice and the system compares them to see if they are the same
#### Visual check
- Manually compare the data entered with the original (document)