Read the data

Data: as usual, the issue is how to read it. As we were saying here, it is crucial to “read the manual”. Besides the issue of data quality, it is important to fully understand how the various figures are defined. The first figure, contained in the daily 6 PM bulletin from Protezione Civile, is the total number of Covid-19 cases defined as currently positive. If incorrectly interpreted, this figure may lead to confusion. Indeed, the number of currently positive cases (abbreviated Cp) is given by an equation relating total cases (Tc), cases where the patient has recovered (R), and deaths (D). This relation can be expressed as

Cp = Tc – R – D

Why is this important? When Protezione Civile refers to the new number of currently positive cases in their bulletins, this is not a data point that is directly measured. Hence the confusion. In some situations, this value might even be negative. If for example there were 1000 new Covid-19 cases, 600 recoveries, and 500 deaths on any given day, the resulting number of currently positive cases would be -100! When reading a data table or tuning into a bulletin, always pay attention to what type of count is being referred to, and most importantly how it is measured.

(Translation by Gabriele Fabozzi)