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<br />tl'.'. 3.-..'...' r <br />. I' ~ >- <br />\...1 ...J..... ~j;j <br /> <br />The log Pearson Type III Distribution - Bulletin 17 data <br /> <br />Karl Pearson proposed a general equation for a distribution that fits many distributions...including normal, <br />beta and gamma distributions by choosing appropriate values for the distributional parameters. A form of <br />the Pearson distribution is known as the Pearson Type III distribution. When used with the loos of the data it <br />is referred to as the log-Pearson TVDe III distribution. <br /> <br />The LP III distribution is significant because it is used by Federal Agencies to model flood flows. The main <br />reference for the procedure used by Federal Agencies is given in Guidelinelines for Determining Flood Flow <br />Frequency, Bulletin 17B, Revised September 1981, U.S. Department of the Interior, Office of Water <br />Coordination <br /> <br />The equations below come from Example 1, Bulletin 17B, Fishkill Creek at Beacon, N.Y. <br /> <br />DATA := <br /> <br />~ <br /> <br />example 1 bulletin 17,txt <br /> <br />DATA = <br /> <br /> 0 1 <br />0 1945 2290 <br />1 1946 1470 <br />2 1947 2220 <br />3 1948 2970 <br />4 1949 3020 <br />5 1950 1210 <br />6 1951 2490 <br />7 1952 3170 <br />8 1953 3220 <br />9 1954 1760 <br />10 1955 8800 <br />11 1956 8280 <br />12 1957 1310 <br /> <br />annual maximum <br />flow data 1945-1968 <br /> <br />i:= 0.. last(DATA(1)) <br /> <br />ft3 <br />f1owi:= DATAi 1'- rename the column in DATA containing flow <br />, sec <br /> <br />[ f10Wj J <br />Yi := In ft3 take the natural log of each flow, divide out units to avoid error <br /> <br /> <br />see <br /> <br />log pearson type III example problem <br />bulletin 17.mcd <br />last save 11/14/2003/12:01 PM <br /> <br />C:\MyFiles\Mathcad application areas <br />\Statistics\log Pearson Type III aka Gamma <br />distribution files\ <br />11/14/2003/12:07 PM <br /> <br />1 of 5 <br />