DATA INPUT AND OUTPUT

INPUT Data capture is collecting data for input to a computer. We try to ensure that the data we collect is accurate and that it is input to the computer without mistakes.

Data capture forms Data can be collected using a data capture form or source document; for example, a questionnaire that is printed on a piece of paper and filled in using a pen or pencil. This method is still widely used although it is now avoided if possible as it is slow and expensive.

For example: A form that might be filled in when reading an electricity meter. After the form is filled in, the data on it is typed into the computer using a keyboard and the input is saved on disk.

When designing a questionnaire or data capture form you should: Clearly state why information is required. Use simple language so people can easily understand it. Layout the form in a straightforward and uncluttered way so that it is easy to see what must be filled in. Say clearly and unambiguously what information must be provided and what is optional.

5. Provide help in answering or examples of how to fill in the form if necessary. 6. Provide enough space for the answer. 7. Show how much space is available for the answer so that users can tailor the length of their answer to the available space. 8. Collect all the information needed, but no more. 9. Avoid asking questions that may not be answered truthfully.

10. Collect information in a way which assists computer input. 11 10. Collect information in a way which assists computer input. 11. Request the information in an intuitive logical order, e.g. name, date of birth…. 12. Encourage people who fill in the form to write their name clearly, and to sign and date the form. This helps ensure that they will fill in the form accurately. 13. Allow people who fill in the form to give yoy their preferred contact details. Giving this will enable you to contact them if they raise issues that need a response.

14. Make it easy for people who fill in the form to submit it 14. Make it easy for people who fill in the form to submit it. Provide instructions on the form that clearly state how the form can be submitted for processing. For e.g. on a printed form sent by post you would need to provide the name and address.

Validation When data is input to a computer, it is a good idea for the computer to check that the data is sensible (no dates of birth in the future, etc.) Checks like this are called validation checks (is the data valid?) Different validation checks can be used on different fields, depending on the type of data being entered

Types of validation Presence Check Range Check Format Check / picture check Field length

Is data actually present in a field, or has it been missed out? Presence check Is data actually present in a field, or has it been missed out?

Example In an electronic form, a person’s telephone number may be a required field and if no data is present this should give rise to an error message.

Range Check Is the data value within a set range?  (E.g. an exam mark should be between 0% and 100%, a month should be between 1 and 12)

A person’s age should be in the range >0 but <150. Example A person’s age should be in the range >0 but <150.

Is an item of text too short or too long? Length Check Is an item of text too short or too long?

Format Check / picture check Is the data in the correct format? (E.g. a date of birth should be entered as dd/mm/yyyy)

Date should be in the form dd/mm/yyyy. Example Date should be in the form dd/mm/yyyy.

Verification Data validation only checks whether the data entered is sensible - it does not mean that the data is the right data. For example, if you are entering a date of birth and you mis-type it… Correct date of birth: 12/11/1982 Date of birth entered: 12/11/1928 . . . you would not see an error, since 12/11/1928 is a valid date of birth. To check that data is the correct value, we use a system called data verification.

Continued There are two methods of data verification... Visual Verification Double-Entry Verification

Visual Verification After the data has been entered a person compares the original data with the data in the computer (either on the screen or using a print-out).  If mistakes are spotted they can be corrected by the person. Proof-reading is quick and simple, but doesn’t catch every mistake.

Double-Entry The data is entered into the computer twice(preferably by two different people).  The computer compares the two sets of data to see if they match. If not it generates an error and a person will need to correct the mistake. Double-entry takes more time and effort, but it catches almost every mistake.

OTHER METHODS OF DATA COLLECTION Direct data entry (DDE) Allows data to be entered directly into the computer, saving time, expense and effort. e.g. input screens Optical mark reader