Technical notes
Interpretation of relative reductions and relative increases
A number of Focus Areas in the National Preventive Health Strategy 2021–2030 (Department of Health and Aged Care 2021a) specify a relative reduction or relative increase to achieve the targets. To aid in the interpretation of this, Table 1 shows what the target proportion is, as calculated from the baseline value using the target relative reduction or increase.
| Focus Area | Target (relative reduction/increase) | Baseline value | Goal |
|---|---|---|---|
| Improving access to and the consumption of a healthy diet | Reduce the average population sodium intake by at least 30% by 2030 | 2017–18: 2,404 mg | 2030: 1682.8 mg |
| Increasing physical activity | Reduce the prevalence of physical inactivity amongst children, adolescents and adults by at least 15% by 2030 | In 2017–18, the proportion of those who were insufficiently physically active were, by age group:
| By 2030, the target proportion of those who are insufficiently physically active are, by age group:
|
| Increasing physical activity | Reduce the prevalence of Australians 15 and over undertaking no physical activity by at least 15% by 2030 | 2017–18: 14.3% | 2030: 12.2% |
| Increasing physical activity | Increase the prevalence of Australians 15+ who are meeting the strengthening guideline by at least 15% by 2030 | In 2017–18, the proportion of those who met the strengthening guideline were, by age group:
| By 2030, the target proportion those who met the strengthening guideline are, by age group:
|
| Reducing alcohol and other drug harm | At least a 10% reduction in harmful alcohol consumption by Australians 14 and over by 2025 and at least a 15% reduction by 2030 | 2019: 32.0% | 2025: 28.8% 2030: 27.2% |
| Reducing alcohol and other drug harm | At least a 15% decrease in the prevalence of recent illicit drug use (14 and over) by 2030 | 2019: 16.4% | 2030: 13.9% |
Age-standardised estimates
Age-standardised rates are used to remove the influence of age when comparing populations with different age structures. Unless otherwise stated, crude rates are reported, and age-standardised rates are used to inform whether comparisons between population group or over time are statistically significant.
The age-standardised proportions in this report have been directly age-standardised to the 2001 Australian standard population.
Relative standard error, margin of error and confidence intervals
The relative standard error (RSE) of an estimate is a measure of the error likely to have occurred due to sampling. The RSEs of the estimates were calculated using the standard errors (SEs):
The margin of error (MoE) at the 95% confidence level for each estimate was calculated using 1.96 as the critical value:
The MoE was then used to calculate the 95% confidence interval (CI) around each estimate:
The 95% CI is a range of values determined by the variability in data, within which there is a 95% chance that the confidence interval will contain the true value of the population quantity being estimated.
Significance testing
Variation or difference in observed values or rates may be due to a number of causes including, among other things, actual differences in the study’s populations and sampling error. A statistical test of significance indicates how incompatible the observed data are with a specified statistical model. To assess whether differences between estimates are incompatible with a null hypothesis that the survey estimates are normally distributed and that there is no difference between the groups being compared, 95% CIs were used.
A difference between estimates was considered statistically significant if the 95% CIs around the estimates did not overlap. Where there was an overlap between 95% CIs, a 95% CI for the difference between estimates was calculated. To do this, the SE of the difference was approximated by:
The 95% CI for the difference between estimates was then calculated as:
If the 95% CI for the difference between estimates included 0, then the difference was not statistically significant. If it excluded 0, then the difference was considered to be statistically significant.
Data sources
The data presented in this report come from multiple data sources, including surveys and administrative data sources. These sources include:
- Australian Bureau of Statistics (ABS)
- Australian Institute of Health and Welfare (AIHW)
- Department of Health and Aged Care
- National Cancer Screening Register