Disclaimer: We have high levels of expertise in statistical modelling. We are not epidemiologists.
Modelling is an imprecise science. As renowned statistician G.E.P. Box once remarked “all models are wrong – but some are useful”. In our earlier post of April 5 (see below) we estimated that the number of diagnosed positive cases in Australia would plateau at 6,195 by April 20, 2020 (day 90 on the plots below). In a subsequent update, it was clear that while the individual state models were doing a reasonable job at describing the tested infection rate, some anomalies were emerging – specifically, Tasmania, WA, and, to a lesser extent, NSW. We have re-fit our models using all available data to April 12, 2020 and these results are shown in the plots below. Based on the updated model predictions, our revised estimate of the total number of diagnosed positive cases will be 6,706 by April 20-24, 2020. The state-by-state breakdown is as follows:
- ACT: 104 cases; max rate of infection occurred on 28/3; estimated flat-line date=20/4
- <predictions validated – actual # cases at 20/4 steady at 104>
- NSW: 3,025 cases; max rate of infection occurred on 27/3; estimated flat-line date=23/4
<flat-line date predicted too early – cases still rising>
- NT: 32 cases; max rate of infection occurred on 30/3; estimated flat-line date=20/4;
<peak overestimated by 4 cases – actual # cases at 20/4 = 28>QLD: 1,035 cases; max rate of infection occurred on 27/3; estimated flat-line date=23/4
<peak overestimated by 9 cases – actual # cases at 23/4 = 1,026>
- TAS: 167 cases; max rate of infection occurred on 4/4; estimated flat-line date=10/5
- VIC: 1,354 cases; max rate of infection occurred on 29/3; estimated flat-line date=25/4
<flat-line date predicted too early – cases still rising (albeit very slowly)>
- WA: 540 cases; max rate of infection occurred on 28/3; estimated flat-line date=24/4
<peak overestimated by 8 cases – actual # cases at 24/4 = 548>
Comment: Tasmania’s situation may be improving with only 2 new cases in the last 4 days. The situation in WA appears to have stabilized although 3 new cases have been reported in the last 2 days.