The optimal control chart selection for monitoring COVID-19 phases: a case study of daily deaths in the USA.

This article focuses on evaluating and applying statistical process control charts, particularly the exponentially weighted moving average (EWMA) chart, to monitor COVID-19 mortality trends in the USA from March 2020 to February 2023. After reviewing control chart applications in epidemiology across multiple countries, the study identified the EWMA chart with a smoothing parameter λ = 0.25 as optimal for detecting shifts in daily COVID-19 deaths and capturing the pandemic's six distinct mortality waves, including the most severe third and fifth waves. The EWMA chart's ability to adjust for seasonality and time-varying factors allowed for detailed monitoring of growth, peak, and decline phases, providing valuable insights for public health decision-making. The study recommends continued use of EWMA charts for mortality surveillance and suggests their broader application in epidemiological monitoring beyond COVID-19 and the USA.