Each data point represents an average of the ozone concentrations for the previous eight hours. For example, the data point graphed at hour 22 (10 p.m.) represents the average of the ozone levels from hour 14 to hour 22 (2 p.m. to 10 p.m.), not the actual ozone level at hour 22. The next data point, graphed at hour 23 (11 p.m.), represents the average of the ozone levels from hour 15 to hour 23 (3 p.m. to 11 p.m.), and so on.


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