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ABOUT MAXIMUM DAILY OZONE IN SAN DIEGO

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 potential harmful chemical to humans, as it will interfere with the 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?

Reference: Data were obtained from CARB's wonderful website, which is a very valuable resource for educators. Look under Air Quality Data: http://www.arb.ca.gov/html/aqe&m.htm

See also the South Coast Air Quality Monitoring District website for southern California: http://www.aqmd.gov

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View the Data

 day in # ozone (ppm) 71 0.053 72 0.050 73 0.038 74 75 0.043 76 0.038 77 0.047 78 0.062 79 0.051 80 0.046 81 0.031 82 0.034 83 0.039 84 0.060 85 0.057 86 0.045 87 0.067 88 0.068 89 0.097 90 0.094 91 0.067 92 0.044 93 0.040 94 0.023 95 0.027 96 0.040 97 0.036 98 0.081 99 0.105 100 0.040 101 0.065 102 0.040 103 0.047 104 0.038 105 0.057 106 0.085 107 0.090 108 0.065 109 0.054 110 0.049 111 0.054 112 0.086 113 0.076 114 0.057 115 0.063 116 0.042 117 0.052 118 0.041 119 0.042 120 0.050 121 0.048 122 0.043 123 0.044 124 0.050 125 0.065 126 0.071 127 0.057 128 0.042 129 0.047 130 0.042 131 0.067 132 0.067 133 0.125 134 0.115 135 0.054 136 0.075 137 0.075 138 0.065 139 0.037 140 0.045 mean ozone 0.0567 sigma 0.0204 min 0.023 max 0.125
 Bin Frequency .02 - .03 2 .03 - .04 8 .04 - .05 21 .05 - .06 13 .06 - .07 12 .07 - .08 4 .08 - .09 3 . 09 - .10 3 .10 - .11 1 .11 - .12 1 .12 - .13 1

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