Laserfiche WebLink
135 NIL <br /> Unofficial Teat(See Printed Volume). Current through date and Register shown on Title Page. <br /> ' CV standard deviation <br /> arithmetic mean <br /> Where: CV=coefficient of variation <br /> CV should be:5 1 to say that the no—trend hypothesis also indicates a stable plume configuration. � <br /> i <br /> Mann—Whitney U Test. This test is equivalent to the Wilcoxon Rank Sum Test <br /> !. Assemble well data for the most recant 8 consecutive quarterly or setn"nnual sampling events for each contaminant <br /> that has exceeded the ES at one or more monitoring wells. Include data from: <br /> a. One or more contaminated monitoring wells near the downgradient plume margin,which may include piezome- <br /> ters, <br /> b. A monitoring well near the source zone,and <br /> c. At least one monitoring well along a flow line between the source zone well and plume margin well. <br /> 2. Eater the data into a DNR supplied spreadsheet or manually assemble the data into a table(e.g.,Table C)in the order <br /> the data was collected. Assign a rank to each sample value,with the smallest value mnked#I and the largest value ranked <br /> #8. i <br /> 3. For purposes of the Mann—Whitney U test,all non—dew values should be assigned a data value of zero(0). <br /> ' Table C <br /> Example Data Set for the Mann--Whitney U Statistical Test <br /> Ran <br /> Benzene k Sum of <br /> Year/Date Concentration(ug/1) Rank lr Year(Wrs) <br /> 1 St Year, 1 St Quatta 160 8 <br /> lr Year,2nd Quarter 130 7 25 <br /> ' 1s'Year 39d Quarter 80 4 <br /> 1st Year,4d'Quarter 100 6 <br /> tad Year, lr Quarter 89 5 <br /> 2nd year�2n4 Quarter 0 1 <br /> god Year,3:d Quarter 53 3 <br /> 20d Year,4's Quarter 24 2 <br /> U=26—Wrs =1 <br /> 4. Sum the ranks for the data in the 19 year: Denote this sum as Wrs(or the Wilcoxon tank sum). <br /> 5. Calculate the U Statistic. U=26—Wrs <br /> 6. Interpreting U Statistic. For 2 groups of 4 samples,at U<_3,the probability that year 2 data show a decrease relative <br /> to year 1 data is at least 90%,and so U<_3 will be acceptable to show that contaminant concentration is declining. <br /> 7. If there at ties in sample data,calculate an average rank value for the tied data and assign this average rank to the tied <br /> sample data. See example in Table D. <br /> I <br /> Reaism.Januar;2001.No.541 <br />