Once we have collected some or all of our data we will need to enter it into your system. It is at this point where many different types of errors can occur, coining the phrase Garbage In, Garbage out (GIGO). Basically if you enter data which contains mistakes and errors then no matter how thorough or clever your queries are you will always get second rate, error laden results.
Once we have collected some or all of our data we will need to enter it into your system. It is at this point where many different types of errors can occur, coining the phrase Garbage In, Garbage out (GIGO). Basically if you enter data which contains mistakes and errors then no matter how thorough or clever your queries are you will always get second rate, error laden results.
To date there is no 100% guaranteed fool proof method for entering data into a system which is completely error free. However there are techniques that you can use to help you reduce the errors to a minimum.
Two of these techniques are called Validation and Verification.
Validation:
Validation is one way of trying to reduce the number of errors in the data being entered into your system.
The validation is performed by the computer at the point when you enter data. It if the process of checking the data against the set of validation rules which you set up when developing your new database or spreadsheet system.
Validation aims to make sure that data is sensible, reasonable,complete and within acceptable boundaries.
If you enter ‘Smithe’ instead of ‘Smith’ or ‘07/08/07’ instead of ‘08/07/07’ no amount of validation in the world will pick up that human error.
So while validation can help to reduce the number of errors when entering data, it cannot stop them.
Read about Types of Database Models.
Methods of Validation:
There are many different methods of validation. The most appropriate method(s) to use will depend upon what data is being entered. The most common methods are listed here.
Presence Check: Checks that data has been entered into a field and that it has not been left blank. E.g. check that a surname is always entered into each record in a database of addresses.
Type Check: Checks that an entered value is of a particular type. E.g. check that age is numeric.
Length Check: Checks than an entered value e.g. surname is no longer than a particular number of characters.
Range Check: Checks that an entered value falls within a particular range. For example the age of a person should be in the range 0 to 130 years.
Format Check: Checks that an entered value has a particular format. E.g. a new-style car registration number should consist of a letter followed by 1 to 3 numbers followed by 3 letters.
Check Digit: A check digit is a digit attached to the end of a string of digits. It is calculated from the other digits and used to help ensure that the whole string is inputted correctly.
Parity Check: Used in data communications to ensure that data is not corrupted when it is sent down a transmission medium such as a telephone line.
Verification
It was mentioned earlier that validation cannot make sure data that you enter is correct; it can only check that it is sensible, reasonable and allowable.
However, it is important that the data in your database is as accurate as possible.
Verification can be used to help make sure that the data in your database contains as few mistakes as possible.
Methods of Verification:
The two most common methods of verification are:
On-Screen Prompts: After a user has entered some data it is redisplayed on the screen. The user is prompted to read the data and confirm that it has been entered correctly. If the user has entered any data incorrectly he should respond that the data is inaccurate and retype the incorrect parts.
Dual Input: This method is used when data is entered at the keyboard. The data to be entered is typed in twice by two different operators. The two copies of the data are then compared. Any differences are detected. The operators will be prompted to retype the sections that differ until both copies agree. When the two copies agree it is assumed by the computer that the data has been entered correctly.
Conclusion
Verification and validation are independent procedures that are used together for checking that a product, service, or system meets requirements and specifications and that it fulfils its intended purpose.
"Validation. The assurance that a product, service, or system meets the needs of the customer and other identified stakeholders. It often involves acceptance and suitability with external customers. Contrast with verification."
"Verification. The evaluation of whether or not a product, service, or system complies with a regulation, requirement, specification, or imposed condition. It is often an internal process. Contrast with validation."
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