Covid-19 Shewhart charts
The Shewhart charts below were motivated by the coronavirus disease 2019 (covid-19) pandemic. They aim to visualize and learn from variation in reported deaths and help countries with decision-making. The 4 Epoch framework provides a method to classify a country’s status in the epidemic curve. The charts are updated daily from the Our World in Data site and the New York Times Github site. The reported deaths are adjusted to account for day-of-the-week variation in reporting. For details on the chart development please read this article. To watch an early presentation on the methodology see here. Charts have been prepared by Gareth Parry, Rocco Perla, Kevin Little, Shannon Provost, and Lloyd Provost.
To read and interrupt the charts: At any one time the chart will show a phase with:
CL (Center Line) – the average of the reported deaths in the phase
UL (Upper Limit) – the upper bound on expected deaths in the phase
LL (Lower Limit) – the lower bound on expected deaths in the phase (may not exist if CL is close to zero)
Blue dot – showing each day’s adjusted reported deaths
Red dot – signal of special cause indicating the beginning of a new phase on the chart