The Statistical Society of Australia (SSA) has delivered a withering assessment of the government's national postal survey on same-sex marriage, saying a simple opinion poll would have been a better measure for gauging the views of all Australians on the issue.
Sixteen million survey forms have been sent to eligible voting Australians with the question: "Do you support a change in the law to allow same-sex couples to marry?" They are due to be returned by November 7, with a result by November 15.
If a "yes" vote is victorious, the government will allow a bill for same-sex marriage to be debated in parliament, while a "no" vote will see any future attempts at reform continue to be blocked.
In a media statement on Wednesday, the SSA criticised the survey, saying it would not reflect the views of all Australians, and could damage the reputation of the Australian Bureau of Statistics (ABS).
The statement is signed by SSA president, Professor Scott Sisson, and the chair of the SSA media and communications committee, Dr Peter Baker.
"If the aim was to understand the views of all Australians, an opinion survey would be more appropriate," it reads. "With a proper survey design and analysis, public opinion can be reliably estimated to a specified accuracy.
"It is the professional opinion of the SSA, the body representing professional statisticians in Australia, that a perhaps more useful government direction could have asked the Australian Statistician to collect statistics to estimate the proportion of all Australians in favour of or against same-sex marriage.
"Such a direction would avoid any chance of misinterpretation, and would arguably be more useful for decision making in terms of understanding the views of Australians as a whole."
Sisson and Baker also noted that an opinion survey could have been implemented at "a fraction of the cost" of the $122 million postal survey.
The ABS is bound to conduct the survey in accordance with the direction from acting special minister of state, Mathias Cormann. It is voluntary to participate, and the one-vote-per-person count will not be weighted (a process in which data is adjusted to represent the demographics of the population being surveyed).
"The SSA is not aware of any official statistics based purely on unadjusted respondent data alone," Sisson and Barker wrote.
"However, under the Government direction, there is no scope to adjust for demographic biases or collect any information that might enable the ABS to even indicate what these biases might be."
Sisson and Baker also say they are worried that the "sensitive and emotive" nature of the debate may lead to uninformed community groups misinterpreting the survey result — and ultimately, won't resolve the tortured issue.
"The SSA is concerned that limitations in the Government direction to the Marriage Law Postal Survey mean that, whatever the result, there will still be considerable uncertainty about the actual views of all Australians on the matter."
Jonathon Palmer, the deputy Australian Statistician who is tasked with completing the postal survey, told BuzzFeed News he disagreed with the claim the survey would fail to resolve the issue.
"It is very possible that, given the high level of interest in this topic, there will be sufficient response to this voluntary survey to provide a clear indication of the views of eligible Australians," he said.
"The ABS is taking considerable measures to ensure the survey process is of high integrity and produces reliable results, and that each eligible Australian has access and opportunity to be able to participate and respond if they wish."
Palmer also said that the survey statement on quality and integrity to be published alongside the results, as well as statistics on demographic participation, would inform how the survey results are used.