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<br />Pm = 1m - 0.31 <br />(N + 0.4) <br /> <br />(1 ) <br /> <br />in which: <br /> <br />P m = exceedance probability estimate for the mth largest <br /> <br />event <br /> <br />m = the order number of the event <br />N = the number of events <br /> <br />For example, to estimate annual exceedance probability of annual maximum discharge: <br /> <br />N = the number of years of data <br /> <br />To express the results as percent-chance exceedance, the results of equation 12.1 are <br />multiplied by 100. <br /> <br />Table 2 shows plotting positions for annual peak discharge on Fishkill Creek. <br />Column 4 of the table shows the discharge values in the sequence of occurrence. <br />Column 7 shows these same discharge values arrange in order of magnitude. Column <br />5 is the order number of each event. Column 8 shows the plotting position. These <br />plotting positions are values computed with equation 1 and multiplied by 100. The <br />values in columns 7 and 8 thus are an estimate of the peak discharge frequency <br />distribution. <br /> <br />7-93 <br />