Time-series modeling of epidemics in complex populations: Detecting changes in incidence volatility over time
Fig 2
Dispersion analysis of weekly COVID-19 case data for Jefferson County, Alabama.
Results for all counties are shown in Fig 3. a: Weekly reported COVID-19 incidence. b: Estimated dispersion parameter () over time. c: Comparison of estimated dispersion (gray) with predicted values from the standard model
, where Ct is reported cases and
the reporting rate at time t. Predictions are shown for fixed
(black) and
(blue), chosen to encompass the range of
expected under variable
. d: Likelihood ratio test (LRT) statistic over time. Statistically significant changes in dispersion (red) correspond to p-values below the Bonferroni-corrected 5% threshold of a chi-square distribution with one degree of freedom.