The PSS and ACMS were designed to provide national statistics relating to the extent and nature of child abuse in Australia. The PSS is used to examine child abuse as a risk factor for adult experiences of violence, while the ACMS is used to understand the five types and experiences of child maltreatment and the impacts of child maltreatment on the mental and physical health of victims.
The two surveys use similar behavioural-based questions to retrospectively collect reported experiences of physical and sexual abuse and who witnessed or were exposed to family and domestic violence as a child (Appendix 2). The conceptual basis for physical and sexual abuse is similar in both surveys. However, the conceptual basis for exposure to family and domestic violence is limited to physical violence in the PSS and is much broader in the ACMS, including physical violence, property damage, emotional and economic abuse.
There are also scope differences between the two surveys with the ACMS collecting data for all experiences of maltreatment before the age of 18 years and the PSS collecting data for experiences before the age of 15 years. For sexual abuse, the ACMS has not yet published further disaggregated data that would enable a comparison with the PSS on rates of sexual abuse perpetrated by adults only.
There are key differences in the sampling method and response rates between the ACMS and the PSS that will have an impact on statistical quality. The ABS can draw on its population address register to use a more robust sampling approach, using the information on the register to ensure appropriate sample composition by design. The PSS uses stratified probability sampling to do this, which involves dividing the population into smaller groups or strata and selecting a cluster of addresses within each stratum at random. Once the responses have been collected, the data are weighted to make the final sample representative of the population as a whole.
In contrast, the ACMS used a sampling method referred to as ‘controlled quota sampling’. This method selects participants through random digit dialling (through a mobile phone sampling frame) and monitors response by age to ensure the final sample represents the age characteristics of the population. The ACMS method is a sound approach for a survey organisation that does not have access to an address register for the population.
The process of either quota sampling (ACMS) or weighting (PSS) is used to make the sample representative of the population with respect to key demographic variables. An age quota is used for ACMS while the PSS is weighted using sex, location and social marital status, in addition to age. The ABS stratification also uses predicted level of assault at an area-level to ensure areas with both high and low levels of experience with assault are represented in the sample.
Irrespective of the sampling method, there might still be bias in reported data due to participation in the survey being influenced by the survey subject matter. There is a risk that people who have experienced maltreatment or assault may be more, or less, likely to choose to participate in the survey than those who have not experienced maltreatment or assault. This is referred to as non-response bias, and in general surveys with a high response rate are less likely to suffer from non-response bias than surveys with a low response rate.
The 4% response rate in the ACMS means that there is a higher likelihood of non-response bias impacting the reliability of the prevalence measures from that study. The combination of a more robust construction of the representative sample and the 52% response rate in the PSS means it is likely to produce more reliable statistics than the ACMS.
A table outlining the key design and scope differences of the two survey approaches is at Appendix 1 and a table outlining the key conceptual and definitional differences of child abuse is at Appendix 2.