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For most states and territories the exclusion of people in sparsely settled areas has only a minor impact on any aggregate estimates that are produced because they only constitute a small proportion of the population. However, this is not the case for the Northern Territory where such persons account for over 20% of the population.
Information was collected only from usual residents. Usual residents were residents who regarded the dwelling as their own or main home. Others present were considered to be visitors and were not asked to participate in the survey.
Information for each household was collected using:
Experienced ABS interviewers were employed to collect HES data. They were given comprehensive training and were provided with detailed written instructions to complement the survey documents.
Interviewers maintained contact with households over a series of visits. The visits and their sequence were as follows:
Computer based systems were used to process the data from the 1998-99 HES with a program known as BLAISE. It was necessary to employ a variety of methods to process and edit the data which reflected the different questionnaires used to collect data from the household, individual and diary components of the surveys. These processes are outlined below.
Coding and input editing of household and individual schedules
Internal system edits were applied in the computer-assisted interview (CAI) questionnaire to ensure the completeness and consistency of the questionnaire. The interviewer could not proceed from one section of the interview to the next until responses had been appropriately completed.
A number of range and consistency edits were programmed into the CAI questionnaire. Edit messages automatically appeared on the screen if the information entered was either outside the permitted range for a particular question, or contradicted information already recorded. These edit queries were resolved on the spot with respondents.
Data from the CAI questionnaires were electronically loaded to the processing database on receipt in the ABS office in each State or Territory. There, checks were made to ensure data for all relevant questions were fully accounted for and that returns for each household and respondent were obtained. Problems identified by interviewers were resolved by office staff, where possible, based on other information contained in the schedule, or on the comments provided by interviewers.
Computer-assisted editing was performed on responses to questions on country of birth, occupation and industry of employment to ensure completeness, and family relationships, to assign individuals’ relationships within household, family and income units.
HES diaries were collected from respondents some two weeks after the initial household interview. They were then dispatched along with the electronic transfer of household and individual schedule information. All reported expenditures in the diaries were entered using the BLAISE Diary Processing System. The BLAISE system helped operators to code diary items into HEC codes. A trigram coder enabled operators to select the appropriate good or service from an alphabetically ordered pick list of options. The system also deleted expenditure recorded in the diaries on items covered by the household questionnaire. For example, the household questionnaire collected information on mains gas payments so any payments coded to HEC code 02010102 (Mains Gas - selected dwelling) were automatically deleted.
The complete list of items classified to each expenditure code is called the HEC coding list and is available for purchase by researchers who need a detailed knowledge of the content of each expenditure code. For example, a researcher may need to know the contents of HEC code 03090301 Potato crisps and other savoury confectionery which the HEC coding list shows to contain bahl chipletts, Burger rings, Cheezels, chips (crisps), chips (not hot), corn chips, Le snack, pretzels, Snack attack and many others. During coding of data, there was a level of manual involvement in adding codes to the coding list for goods not already listed and for variant spelling and punctuation of reported expenditures.
A range of processes was applied to the diary information to check that expenditure items as well as values had been recorded; that specific values were correctly coded if they were unusually high or low; that errors had not occurred in coding; and that relationships between household and diary information were consistent. A Query Resolution System ensured that:
A range of edits was also applied to the household, individual and diary information to double check that logical sequences had been followed in the questionnaires; that specific values lay within expected ranges; and that relationships between items were consistent.
After unusually high expenditure and income values (termed statistical outliers) were investigated to determine whether there had been errors in entering the data, such values were also examined for their effect on total income and expenditure estimates for Australia. As a result, a small number of outliers were winsorised, that is, the values were reduced to the next highest recorded value. Winsorisation aims to improve the reliability of estimates and was considered where analysis showed that the unaltered values significantly affected the distribution of the Australia level total household expenditure and income estimates.