MEASURES TO MAXIMISE RESPONSE

In any sample survey, responses should ideally be obtained from all selected units, however there will always be some non-response; for example, when people cannot be contacted or are contacted but cannot be interviewed, or refuse to participate in the survey. It is important that response be maximised in order to reduce sampling variability and avoid biases. Biases can arise if those people selected for the survey but who do not respond have characteristics different to those who did respond.

The ABS sought the willing cooperation of selected households. Measures taken to encourage respondent cooperation and maximise response included:

• advance notice of a household's selection in the 2011-13 AHS by letter, explaining the purposes of the survey, its official nature and the confidentiality of the information collected. The letter stated that an ABS interviewer would visit, and provided an ABS contact number for more information if required. An information brochure on the survey was also provided.
• stressing the importance of participation in the survey by the selected households and residents, explaining that they represented a number of other households, both geographically and demographically; that is, that their household represented other households similar in size, composition and location, and that they themselves represented other people with similar occupations, lifestyles and health characteristics. The cooperation of selected persons was important to ensure all households/persons were properly represented in the survey and properly reflected in survey results.
• stressing the importance of the survey to the planning and provision of health services and facilities to meet Australia's health needs.
• stressing the confidentiality of all information collected. The confidentiality of data is guaranteed by the Census and Statistics Act 1905. Under the provisions of this Act, the ABS is prevented from releasing any identifiable information about individuals or households to any person, organisation or government authority.

Through call-backs and follow-up at selected dwellings, every effort was made to contact the occupants of each selected dwelling and to conduct the survey in those dwellings. Interviewers made five call-backs before a dwelling was classified as a ‘non-contact’ (three call-backs in non-metropolitan areas). Call-backs occurred at different times of the day to increase the chance of contact. Once contact had been made at a dwelling, the interviewer completed all necessary questionnaires where possible. If any persons who were selected to be included in the survey were absent from the dwelling when the interviewer called, arrangements were made to return and interview them. Interviewers made return visits as necessary in order to complete questionnaires for selected persons in scope of the survey. In some cases, a selected respondent within a dwelling could not be contacted or interviewed, and these were classified as individual non-contacts.

In cases where a respondent initially refused to participate in the survey or there was non-contact due to no one being home at the time of the visit, a follow-up letter was sent to that household. A second visit was made to the respondent to explain the aims and importance of the survey, and to answer any particular concerns the respondent may have had. No further contact was made with the respondent if they refused at the second approach to participate. Persons missed from the survey through non-contact or refusal were not replaced in the sample, except in the Northern Territory where an additional 53 households for NHS and 34 households for NNPAS were approached and added to the sample between December 2011 and March (NHS) / May (NNPAS) 2012.

Procedures were also undertaken to maximise the response rate for the voluntary biomedical component. In the first instance, interviewers highlighted the major personal and wider community benefits to the respondent. These benefits included:

• receiving personal, comprehensive information about their health
• identifying areas of need in the community
• providing long term health benefits to the Australian population, through a better understanding of how our lifestyles and diets impact on our health.

Interviewers were further trained to provide responses to a range of questions, as well as to direct respondents to the Frequently Asked Questions page on the AHS website. In addition, a 1800 AHS Information line was available during business hours for any AHS related queries. In the NNPAS during the CATI, interviewers also took the opportunity to remind respondents who had expressed an interest in participating in the biomedical component about attending a collection centre to provide samples.

For the respondents who consented to the voluntary biomedical component but had not yet attended a collection clinic, a follow-up reminder process was in place. This process took the form of phone calls or letters arranged ten days apart from the interview date. Also, home visits and temporary clinics were offered to participants in certain circumstances to maximise participation rates, particularly in remote areas and for those who were incapacitated.

So as not to be out of pocket for travel, child-care or time off work, biomedical participants were able to claim a reimbursement of $50 paid into an Australian bank account.

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