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4 A supplementary health survey of Aboriginal and Torres Strait Islander people was conducted in association with the 2001 NHS. Information about that survey, together with summary results is published separately in National Health Survey: Aboriginal and Torres Strait Islander Results, Australia, 2001 (cat. no. 4715.0).
SCOPE OF THE SURVEY
5 The NHS was conducted in a sample of 17,918 private dwellings across Australia. Both urban and rural areas in all states and territories were included, but sparsely settled areas of Australia were excluded. Non private dwellings such as hotels, motels, hostels, hospitals, nursing homes and short-stay caravan parks were not included in the survey.
6 Within each selected household, a random sub-sample of usual residents was selected for inclusion in the survey as follows:
8 The following groups were excluded from the survey:
9 Trained ABS interviewers conducted personal interviews with selected residents of sampled dwellings. One person aged 18 years and over in each dwelling was selected and interviewed about their own health characteristics. An adult resident, nominated by the household, was interviewed about all children aged 0-6 years and one selected child aged 7-17 years in the dwelling. Adult female respondents were invited to complete a small additional questionnaire covering supplementary women's health topics.
SAMPLE SIZE AND SELECTION
WEIGHTING, BENCHMARKING AND ESTIMATION
13 Weighting is the process of adjusting results from a sample survey to infer results for the total population. To do this, a 'weight' is allocated to each sample unit. The weight is a value which indicates how many population units are represented by the sample unit.
14 The first step in calculating weights for each person was to assign an initial weight, which was equal to the inverse of the probability of being selected in the survey. For example, if the probability of a person being selected in the survey was 1 in 600, then the person would have an initial weight of 600 (that is, they represent 600 others).
15 The weights were calibrated to align with independent estimates of the population of interest, referred to as 'benchmarks', in designated categories of sex by age by area of usual residence categories. Weights calibrated against population benchmarks compensate for over or under-enumeration of particular categories of persons and ensure that the survey estimates conform to the independently estimated distribution of the population by age, sex and area of usual residence, rather than to the distribution within the sample itself.
16 The survey was benchmarked to the estimated population living in private dwellings in non-sparsely settled areas at 30 June 2001 based on results from the 2001 Census of Population and Housing. Hence the benchmarks relate only to persons living in private dwellings, and therefore do not (and are not intended to) match estimates of the total Australian resident population (which include persons living in non-private dwellings, such as hotels) obtained from other sources.
17 Survey estimates of counts of persons are obtained by summing the weights of persons with the characteristic of interest. Estimates of non-person counts (e.g. days away from work) are obtained by multiplying the characteristic of interest with the weight of the reporting person and aggregating.
18 Many health characteristics are age-related and to enable comparisons across population groups (e.g. between states) the age profile of the populations being compared needs to be considered. The age standardised percentages are those which would have prevailed should the actual population have the standard age composition. In this publication the standard population is the benchmark population; i.e. the population at 30 June 2001 based on the 2001 Census of Population and Housing, adjusted for the scope of the survey. It should be noted that minor discrepancies in totals may occur between standardised and non-standardised estimates or percentages, as a result of the standardisation process.
RELIABILITY OF ESTIMATES
19 The estimates provided in this publication are subject to sampling and non-sampling error.
20 Sampling error is the difference between the published estimates, derived from a sample of persons, and the value that would have been produced if all persons in scope of the survey had been included. For more information refer to the Technical Notes. In this publication, estimates with a relative standard error of 25% to 50% are preceded by an asterisk (e.g. *3.4) to indicate that the estimate should be used with caution. Estimates with a relative standard error over 50% are indicated by a double asterisk (e.g.**0.6) and should be considered unreliable for most purposes.
NON SAMPLING ERROR
21 Non-sampling error may occur in any data collection, whether it is based on a sample or a full count such as a census. Sources of non-sampling error include non-response, errors in reporting by respondents or recording of answers by interviewers, and errors in coding and processing data.
22 Non-response occurs when people cannot or will not cooperate, or cannot be contacted. Non-response can affect the reliability of results and can introduce a bias. The magnitude of any bias depends upon the rate of non-response and the extent of the difference between the characteristics of those people who responded to the survey and those who did not.
23 The following methods were adopted to reduce the level and impact of non-response:
24 By careful design and testing of questionnaires, training of interviewers, asking respondents to refer to records where appropriate, and extensive editing and quality control procedures at all stages of data processing, other non-sampling error has been minimised. However, the information recorded in the survey is essentially 'as reported' by respondents, and hence may differ from information available from other sources, or collected using different methodology. In particular it should be noted that:
RECENT INJURIES MODULE
25 The recent injuries module refers to selected events occurring in the four weeks prior to interview which resulted in injury, and which in turn resulted in medical consultation or treatment, or a reduction in usual activities. The types of events included were:
26 The topic aimed to cover all injuries, from minor scrapes and cuts through to serious injuries such as broken bones and burns, and included birth injuries if these occurred in the previous four weeks. Detailed information was collected about those events resulting in injury for which some action was taken. Food poisoning and minor insect bites were not regarded as an injury for the purposes of this survey.
27 The data items included in the NHS module on recent injuries are based on the National Minimum Data Set for Injury Surveillance in the National Health Data Dictionary. They include items describing the event, the type of injury and its bodily location, the place of occurrence and the activity when injured.
28 Respondents were asked (with the aid of prompt cards) whether any of the events listed above had happened to them in the previous four weeks and if so, whether those events had resulted in the respondent taking one or more of the following actions:
29 For those who reported an event for which one or more of those actions was taken, information was collected to establish the number and types of event(s) which had occurred in that period. Further information was then collected about each of the three most recent events in that four-week period. This information covered details of the event (activity at the time of the injury, and location of event) and consequences of the event (type and bodily location of injury, medical treatment and days of reduced activity resulting from the injury). Prompt cards were used to assist respondents in reporting type of injury, activity at time of event, location of event, and medical consultation arising from the event.
30 Respondents reporting an injury while working for an income were asked if this was in the same occupation as previously reported in the interview; that is, occupation in the main job the respondent had at the time of the survey. For those not in the labour force, not currently employed, or who have changed occupation since their injury, details of the occupation at the time of the injury were not recorded.
31 A small number of cases were recorded in the survey where after the initial screening questions, it was found that no injury had resulted from the reported event. In these cases no further information about the event or consequences of the event were recorded. These are included in counts of events, but not in counts of injuries or injury events; see diagram later in this section.
32 Information was collected for all persons in scope of the survey.
33 Items available for reported events:
35 Points to be considered in interpreting data for this topic include the following:
LONG-TERM MEDICAL CONDITIONS
36 All reported long-term medical conditions were coded to a list of approximately 1,000 condition categories which was prepared for this survey. Information about medical conditions classified at this level of detail will not generally be available for output from the survey; however, they can be regrouped in various ways for output. Three standard output classifications developed by the ABS for this survey are available:
37 In this publication, medical conditions data from the 2001 NHS are shown classified to the ICD-10-based classification, or variants of that classification.
LONG-TERM MEDICAL CONDITIONS: REPORTED CAUSE
38 This topic refers to the cause; work-related or as a result of an injury (including injury at work) of current long-term conditions, as reported by respondents.
39 Respondents who earlier in the survey had reported one or more current long-term conditions were asked whether that/any of the condition(s) was work related , and whether that/any of the condition(s) was the result of an injury. The type of condition was recorded in either case; provision was made to record up to five conditions as work-related and five conditions as due to an injury. The same condition may have been reported and recorded as both work related and due to an injury.
40 Respondents who reported one or more conditions as due to an injury were asked, in respect of each condition, whether the injury was received while at work (for those aged 15 years and over) or at school (for those aged under 15 years), in a motor vehicle accident or during exercise or sport.
41 Information was collected in respect of all persons for whom one or more current long-term condition had been reported.
42 Points to be borne in mind in interpreting data from the survey relating to the reported cause of long-term conditions:
43 In this publication, survey results are shown compiled for Australia, individual states and the ACT.
RESULTS OF THE SURVEY
COMPARABILITY WITH PREVIOUS NATIONAL HEALTH SURVEYS
44 Summary results of the three NHSs were published in National Health Survey: Summary of Results, 1989-90, 1995 and 2001 (cat. no. 4364.0). A range of other publications was also released from each of these surveys; see paragraph 51.
45 The 2001 NHS is similar in many ways, particularly to the 1995 NHS, however there are important differences in sample design and coverage, survey methodology and content, definitions and classifications. These will affect the degree to which data are directly comparable between the surveys.
46 The main differences between the 1995 and 2001 NHSs which may affect comparability of data presented in this publication with previous publications are shown below. Differences in the recent injuries module and long-term conditions caused by injury or injury event meant that comparability between the 1995 and 2001 NHSs was not possible. For example:
HEALTH PRODUCTS AND SERVICES
49 Users wishing to undertake more detailed analysis of the survey data may apply for access to either the BASIC or EXPANDED NHS Confidentialised Unit Record Files (CURFs). All clients wishing to access the NHS CURFs should refer to the 'Access to ABS CURFs' section located on the ABS web site, and read the Responsible Access to ABS Confidentialised Unit Record Files (CURFs) Training Manual, and other relevant information, before downloading the Application and Undertaking to apply for access. Any queries relating to Conditions of Sale should be referred to firstname.lastname@example.org
50 Special tabulations are available on request. Subject to confidentiality and sampling variability constraints, tabulations can be produced from the survey incorporating data items, populations and geographic areas selected to meet individual requirements. These can be provided in printed or electronic form. A list of data items available from the survey is available free of charge on this site. Further information about the survey and associated products is available from the National Information and Referral Service. Details are listed at the front of this publication.
51 Other ABS thematic publications and web-based papers which may be of interest are shown below. Most of these are available at <www.abs.gov.au>:
National Health Survey, Summary Results, Australian States and Territories, 1995 and 2001, cat. no. 4368.0
National Health Survey, Users' Guide, 1989-90, 1995 and 2001, cat. no. 4363.0
National Health Survey, Private Health Insurance, Australia, 1995, cat. no. 4334.0
National Health Survey: Diabetes, Australia, 1995, cat. no. 4371.0
National Health Survey: Cardiovascular and Related Conditions, Australia, 1995, cat. no. 4372.0
National Health Survey: Asthma and Other Respiratory Conditions, Australia, 1995, cat. no. 4373.0
National Health Survey: Injuries, Australia, 1995, cat. no. 4384.0
National Health Survey: SF36 Population Norms, Australia, 1995, cat. no. 4399.0
Mental Health and Wellbeing of Adults: Profile of Adults, Australia, 1997, cat. no. 4326.0
National Survey of Mental Health and Wellbeing of Adults: Users' Guide, 1997, cat. no. 4327.0
National Nutrition Survey: Selected Highlights, Australia, 1995, cat. no. 4802.0
National Nutrition Survey: Foods Eaten, Australia, 1995, cat. no. 4804.0
National Nutrition Survey: Nutrient Intakes and Physical Measurements, Australia, 1995, cat. no. 4805.0
National Nutrition Survey: Users' Guide, 1995, cat. no. 4801.0
Children's Health Screening, 1995, cat. no. 4337.0
Children's Immunisation Survey, Australia, 1995, cat. no. 4352.0
Disability, Ageing and Carers, Australia: Summary of Findings, 1998, cat. no. 4430.0
Breastfeeding in Australia, cat. no. 4810.0.55 .001
Occasional Paper: Vaccination Coverage in Australian Children - ABS Statistics and the Australian Childhood Immunisation Register (ACIR), cat. no. 4813.0.55.001
Occasional Paper: Measuring Dietary Habits in the 2001 National Health Survey, Australia, cat. no. 4814.0.55.001
National Health Survey: Private Health Insurance, Australia, cat. no. 4815.0.55.001
Occasional Paper: Long-term Health Conditions - A Guide to Time Series Comparability From The National Health Survey, Australia, cat. no. 4816.0.55.001
Information Paper: Use of the Kessler Psychological Distress Scale in ABS Health Surveys, Australia, cat. no. 4817.0.55.001
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