1331.0 - Statistics - A Powerful Edge!, 1996
ARCHIVED ISSUE Released at 11:30 AM (CANBERRA TIME) 31/07/1998
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DATA PROCESSING
DATA CODING Before raw data is entered into a computer it may need to be coded. Coding involves labelling the responses in a unique and abbreviated way (often by simple numerical codes). The reason raw data are coded is that it makes data entry and data manipulation easier. Coding can be done by interviewers in the field or by people in an office. A closed question implies that only a fixed number of predetermined responses are allowed, and these responses can have codes affixed on the form. An open question implies that any response is allowed, making subsequent coding more difficult. One may select a sample of responses, and design a code structure which captures and categorises most of these. DATA INPUT The keyboard of a computer is one of the more commonly known input, or data entry, devices in current use. In the past, punched cards or paper tapes have been used. Other input devices in current use include light pens, trackballs, scanners, mice, optical mark readers and bar code readers. Some common everyday examples of data input devices are:
The ABS gathers data from censuses and surveys. The method of data entry varies, depending on the type or method of collection.
DATA EDITING Before being presented as information, data should be put through a process called editing. This process checks for accuracy and eliminates problems that can produce disorganised or incorrect information. Data editing may be performed by clerical staff, computer software, or a combination of both; depending on the medium in which the data is submitted. Some editing processes are: Validity check: ensures that data fall within set limits. For example, alphabetic characters do not appear in a field that should have only numerical characters, or the month of year is not greater than 12. Verification check: checks the accuracy of entered data by entering it again and comparing the two results. Consistency check: checks the logical consistency of answers. For example, an answer stating never married should not be followed by one stating divorced. Data editing should detect and minimise errors such as:
Inaccuracy in responses may result from carelessness or a deliberate effort to give misleading answers. Answers needing mental calculations may result in errors, for example: when converting days into hours, or annual income into weekly income. EXAMPLE 1. This example of data to be edited shows an inaccurate response. By carefully reading this section of the ABS Labour Force Survey form you should be able to detect a very inaccurate response! Question 34A shows that Person 1 said they worked on every day of the previous week. Question 34B shows there was no time off, and Question 34C says some overtime was also worked. However, Question 34D says that all of this amounted to less than one hour of time worked! The answers to individual questions look acceptable. It is only by comparing them with each other that you find if one or more are wrong. This cross-checking is only one type of edit. It could be performed either by clerical staff or editing software. It indicates that further action should be taken. In the previous example, the interviewer will get in touch with the household and re-check how many days and hours were worked by Person 1. DATA MANIPULATION After editing, data may be manipulated by computer to produce the desired output. The software used to manipulate data will depend on the form of output required. Software applications such as word processing, desktop publishing, graphics (including graphing and drawing), databases and spreadsheets are commonly used. Following are some ways that software can manipulate data:
Processing data provides useful information called output. Computer output may be used in a variety of ways. It may be saved in storage for later retrieval and use. It may be laser printed on paper as tables or charts, put on a transparent slide for overhead projector use, saved on floppy disk for portable use in other computers, or sent as an electronic file via the internet to others. Types of output are limited only by the available output devices, but their form is usually governed by the need to communicate information to someone. For whom is output being produced? How will they best understand it? The answers to these questions help determine one’s output type.
EXERCISES
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