Using the Critical Difference
Most communities will see some change in the proportion of children who are developmentally vulnerable, at risk or on track reported compared to previous years. In some cases this will be small and in others it will be more substantial.
Critical difference enables the tracking of changes over time and calculates whether a change in results is significant or not. The critical difference is the minimum level of change required between two cycles to be statistically significant. Significant, in this case, means a level of certainty that the change did not occur by chance. The critical difference varies depending on the number of children in a community, and the AEDC indicator of interest.
The Critical Difference Calculator for the AEDC will calculate the observed and critical difference and help interpret results.
Further information on the critical difference is available in the Technical Report: Calculation of the Critical Difference.
The critical difference calculation takes into account the number of children included in the AEDC data collections and variation between teachers in the way they assess children.
Number versus proportion
When comparing the proportion of children developmentally vulnerable, at risk or on track across collections, it is important to consider the number and proportion of children.
For smaller communities, results should be interpreted with caution as it only takes a change in a few children to have a big impact on the proportion of children who are developmentally vulnerable, at risk or on track.
A number of resources are available to help understand the critical difference and interpret the AEDC results. These include: