Description:
Ozone (O3) is a compound of oxygen found both high in the stratosphere (the "good" ozone blocking harmful ultraviolet radiation) and low in the troposphere (the "bad" ozone that is the main part of photochemical smog). Ozone is a potentially harmful chemical to humans, as it will interfere with respiration, even at very low concentrations. Ozone causes inflammation of airways that can reduce lung capacity and can result in permanent damage to lung tissue. The EPA has established a federal standard for ozone concentration in the lower atmosphere at .12 ppm (average concentration over 1 hour).
Air samples taken on Overland Avenue in downtown San Diego during June, July, and August of 1998 were analyzed for ozone and compiled by the California Air Resources Board (CARB). The data were reported in several different fashions. Maximum daily concentration of ozone measured over a 1 hour period are given in the table and shown in the diagram.
The data can be displayed and analyzed using a histogram, which shows a skew-symmetric distribution of maximum ozone values measured on 70 different days during the summer of 1998 in San Diego. Skew symmetric distributions are quite useful in illustrating to the student the differences between the mean, median, and mode. The mean ozone maximum is much lower than the federal standard, however, there was one day in August when the EPA standard was exceeded.
The choice of graphical representation can obscure or illuminate the data; students should learn that graphs are no substitute for the original data. Is there some way of graphically representing this data set to "hide" the one value that exceeds the federal standard?
