Data collection

Information in the 2017-18 NHS was obtained by trained ABS interviewers, through Computer Assisted Personal Interview (CAPI), with all selected members of in-scope households (see Scope and Sample Design and Selection sub-sections for further information). For the purposes of the NHS, a household was defined as one or more persons, at least one of whom is aged 18 years and over, usually resident in the same private dwelling.

Interviewers

Interviewers were recruited from a pool of trained interviewers with previous experience on ABS household surveys where possible, and undertook further classroom training and a requirement to satisfactorily complete home study exercises. Training emphasised understanding of survey concepts, definitions and procedures to ensure that a standard approach was employed by all interviewers. Regular communication between field staff and survey managers was maintained throughout the survey via database systems set up for the survey.

Interviewers were allocated a number of dwellings (a workload) at which to conduct interviews. The size of the workload was dependent upon the area involved and whether or not the interviewer was required to live away from home to collect the data. Interviewers living close to their workload area in urban areas usually had larger workloads. Overall, workloads were to be enumerated over a two week period and averaged in size between 20-25 dwellings.

Interviews

Household Contact Details Form (HCDF)

Prior to enumeration, all selected households were sent out pre-approach material by mail that consisted of the following:

• Guide, sent to the dwelling 12 days prior to enumeration
• Registration letter and Leaflet, sent to the dwelling 9 days prior to enumeration
• Reminder letter, sent 5 days prior to enumeration.

The Guide informed respondents of their selection in the survey and provided information regarding the background to the survey, interview process and confidentiality provisions under the Census and Statistics Act 1905.

The Registration and Reminder letters contained the log-on credentials to register and complete an online Household Contact Details Form (HCDF). The HCDF was used to gather respondent contact details and best time to call information to arrange an interview. It was available to respondents throughout the enumeration period. This information was used to help interviewers plan their workloads and save unnecessary trips to selected dwellings.

This approach was not possible for a small number of households for which the ABS did not have an adequate postal address. For non-deliverable households, Interviewers left a copy of the Guide and a Non-deliverable Letter informing respondents of their selection in the survey and advising them that an Interviewer would visit to arrange a suitable time to conduct the survey interview.

Household details


General characteristics of the household were obtained from any responsible adult (ARA) member of the household, either over the phone (if the respondent had registered and provided their contact details via the HCDF) or upon the first face-to-face contact with the household. This information included the number and basic demographic characteristics of usual residents of the dwelling (e.g. age and sex), and the relationships between those people (e.g. spouse, son/daughter, not related). The ARA was also asked to nominate the person in the household who was best able to provide information about children in the household.

From the information provided by the ARA regarding household composition, those persons in scope of the survey were determined, and, on a random basis, one adult and one child (where applicable) were selected for inclusion in the survey.

If the dwelling contained no usual residents aged 18 years or more, no further information was collected from that household.

If the dwelling contained more than fifteen usual residents, all of whom were in scope, then it was determined whether there was more than one family group living in the dwelling, and each family group was then treated as a separate household.

Personal and Proxy Interviews

A personal interview was conducted with the selected adult (where possible), and an adult was asked to respond on behalf of the selected child aged under 15 years.

In some instances, adult respondents were unable to answer for themselves due to significant long-term illness or disability. In these cases, a person responsible for them was interviewed on their behalf, provided the interviewer was assured that this was acceptable to the selected person. Where possible, the respondent was still present during the interview and physical measurements were taken where appropriate.

In limited circumstances where there were language difficulties, other persons in the household may have acted as an interpreter if this was suggested by the respondent. If not, arrangements were made, where possible, for the interview to be conducted either by an ABS interviewer fluent in the respondent’s own language, or with an ABS interpreter.

Where permission was granted by a parent or guardian, children aged 15-17 years were interviewed in person. If permission was not granted, questions were answered by an adult, who may or may not have been the selected adult respondent in the household. The person answering on behalf of the 15-17 year old is referred to as the Child Proxy. Interviews where a Child Proxy was used are identified by the 'Proxy status for children' data item (see Administrative tab of Data Item List). There are also data items available which identify parent presence or proxy use at other stages of the interview, including 'Presence of parent during alcohol questions' and 'Presence of parent during smoking questions' data items (see Administrative tab of Data Item List)).

Certain modules that required personal reflection or that the respondent was physically present were not part of the interview in cases where a proxy was answering and the selected person was not present. These included:

• Physical measures (blood pressure, height, weight and waist measurements)
• Mental wellbeing
• Self-perceived body mass
• Self-reported height and weight
• Dwelling tenure and characteristics.

Interviewers were instructed to record whether a proxy interview was being undertaken, and whether the respondent was providing the answers.

To obtain a personal interview with appropriate respondents, interviewers made appointments as necessary with the household. In cases where the HCDF was completed, the Household Form was completed by telephone and the ARA was informed of the selected respondents so that appointments for personal interviews could be arranged. All interviews were, however, conducted face-to-face. Interviews may have been conducted in private or in the presence of other household members according to the wishes of the respondent.

Interviews were conducted on Sundays only when specifically requested by a respondent. Although it is desirable to spread interviews across all days of the week, interviews were conducted on days that suited respondents.

Questionnaire

The 2017-18 NHS utilised a Computer Assisted Personal Interview (CAPI) instrument to collect the data.

The CAPI instrument allows:

• Data to be captured electronically at the point of interview, which reduces the cost, logistical, timing and quality issues associated with transport, storage and security of paper forms, and transcription/data entry of information from forms into electronic format
• The ability to use complex sequencing to define specific populations for questions, and ensure word substitutes used in the questions were appropriate to each respondent's characteristics and prior responses
• The ability, through data validation (edits), to check responses entered against previous responses, reduce data entry errors by interviewers, and enable seemingly inconsistent responses to be clarified with respondents at the time of interview. The audit trail recorded in the instrument also provides valuable information about the operation of particular questions, and associated data quality issues
• Some derivations to occur in the instrument itself, assisting in later processing
• Auto-coding systems to be incorporated, reducing interview and processing time
• Data to be delivered in an electronic format compatible with ABS data processing facilities.

The questionnaire was field tested via cognitive testing and a dress rehearsal to ensure:

• Data was obtained in an efficient and effective way
• There was minimum respondent concern about the sensitivity or privacy aspects of the information sought
• There was effective respondent/interviewer interaction and acceptable levels of respondent burden
• Operational aspects of the survey were satisfactory; e.g. arrangement of topics, sequencing of questions, adequacy and relevance of coding frames, etc.

The questionnaires employed a number of different approaches for recording information at the interview.

• Questions where responses were classified by interviewers to one or more of a set of predetermined response categories. This approach was used for recording answers to the more straightforward questions, where logically a limited range of responses was expected or where the focus of interest was on a particular type or group of responses (which were listed in the questionnaire, with the remainder being grouped together under ‘other’).
• Questions where responses were recorded by interviewers as reported, for subsequent classification and coding by office staff during processing. This style of question was used for potentially more complex topics such health conditions or medications used.
• Questions asked in the form of a running prompt; that is, predetermined response categories were read out to the respondent one at a time until the respondent indicated agreement to one or more of the categories (as appropriate to the topic) or until all the predetermined categories were exhausted.
• Questions asked in association with prompt cards. Printed lists of possible answers to the question were shown the respondent who was asked to select relevant responses. Listing a set of possible responses (either in the form of a prompt card or a running prompt question) served to clarify the question or to present various alternatives, to refresh the respondent’s memory and at the same time assist the respondent to select an appropriate response.
• Procedures for obtaining the measured height, weight, waist circumference and blood pressure of respondents. Interviewers took the physical measurements using a variety of techniques (see: Body mass and physical measurements and Blood pressure chapters for more information).

To ensure consistency of approach, interviewers were instructed to ask the interview questions exactly as written. In certain areas of the questionnaire however, interviewers were asked to use indirect and neutral prompts at their discretion, where the response given was, for example, inappropriate to the question asked or lacked sufficient detail necessary for classification and coding. This occurred particularly in relation to type of medical condition where interviewers were asked to prompt for a condition if a treatment or symptom was initially reported.

The questionnaire was designed to be administered using standard ABS procedures for conducting population interview surveys, with regard to the particular aims of the survey and the individual topics within it, and the methodological issues associated with those topics. Other factors considered in designing the questionnaire included the length of individual questions, the use of easily understood words and concepts, the number of subjects and overall length of the questionnaire, and the sensitivity of topics. Where appropriate, previous ABS questions on the topics covered were adopted.

The 2017-18 NHS questionnaire included:

• Household information - basic demographic data about usual residents of the household (e.g. sex, age, country of birth, Indigenous status, marital status) and details of the relationship between individuals in each household. This information was obtained from the ARA. The data was also used to enable the selection of respondents in the dwelling. Information was also recorded on the calls made to the dwelling by the interviewer, and the subsequent response status of the household in the survey (e.g. fully responding, refusal, vacant dwelling, etc.).
• Personal (or proxy) Adult Interview - information was collected from the selected adult or their proxy about demographic, socio-economic and health characteristics (e.g. long-term health conditions and risk factors). Physical measurements (height, weight, waist and blood pressure measurements) were taken except for adult proxy interviews where the selected person was not present.
• Personal (or proxy) Child Interview - information was collected on selected demographic and health characteristics. Questions on socio-economic characteristics, smoking and alcohol were not asked of children aged under 15 years, and questions on levels of psychological distress were not asked of persons aged under 18 years. Physical measurements (height, weight and waist measurements) were taken for children aged 2 years and older.

A copy of the 2017-18 NHS Questionnaire and Prompt cards are available through the Downloads page of this product.