data the datat is for covid 2020 AND 2021 for the USA. Time series data for COVID-19 confirmed cases in the United States for the years 2020 and 2021 can be obtained from the CSSE (Center for Systems Science and Engineering) at Johns Hopkins University public archive data The data of PM2.5 is often reported using the Air Quality Index (AQI), which provides an overall measure of air quality based on various pollutants, including PM2.5. However, the AQI is a dimensionless index and not directly usable for quantitative analyses due to its scale and unitless nature.To facilitate statistical analysis and comparisons, researchers often convert AQI values to a more quantitative and usable unit such as micrograms per cubic meter (µg/m³) using appropriate conversion equations.