I thought this was a fantastic post and I was very much interested in looking at the daily trends in testing data.
Unfortunately, I found that there is a great deal of noise in the state level testing reports. Some states are reporting 100% positive rates in the last day.
Import["https://covidtracking.com/api/states/daily", "RawJSON"] /.
Null -> Missing // Dataset;statesDailyTracking[Select[#state == "MD" &]][1 ;; 5])
I do not know how to paste my output here.
However, it is clear that the way that testing is being performed unevenly across the country by state (and perhaps by county within state) makes the analysis of serial testing data much more complicated than just looking at the rolled up countrywide results.
Nothing about this data is easy, but live data almost always has difficulties.