The air quality index explained: What air quality is bad?

What is the Air Quality Index?

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SOLVED: Daily air quality is measured by the air quality index (AQU) reported by the Environmental Protection Agency: This index reports the pollution level and what associated health effects might be concern The index Is calculated for five major air pollutants regulated by the Clean Air Act and takes values from 0 to 300 where a higher valle indicates lower air quality: AQl was reported for sample of 91 days in 2011 in Durham, NC . The relative frequency histogram below shows the distribution