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GG 313 Homework 4 Due 9/20/05 1. Water samples from two rivers have been analyzed for Mercury contamination. The following are the results of the analysis (in ppm): River A : 8.6 10.5 9.2 9.4 8.9 8.3 10.9 10.0. River B : 10.6 11.2 12.1 11.5 12.6 10.1 10.8 12.1 11.4. (a) At the 95% confidence, do these samples have the same standard deviations? (b) At the 95%confidence, do these samples support the hypothesis that the average mercury contamination is higher in river B than in river A? Note that you can use matlab to calculate the mean and standard deviation. If x is a vector of values (e.g., x=[8.6 10.5 9.2 9.4 8.9 8.3 10.9 10.0]), mean(x) will calculate the mean and std(x) will calculate the standard deviation. Type help mean and help std to get more information. 2. Seamount densities in 6 areas are proposed to come from a single random process with equal probability in each area. The areas are surveyed, and the following numbers of seamounts are obtained in each: 1 had 121, 2 had 107, 3 had 98, 4 had 132, 5 had 136, and 6 had 118. At the 0.05 level of significance, do these results support the hypothesis? 3) Using the two coin-toss data sets obtained in class today, determine: A) Do they have the same means at 95% Confidence? B) Do they have the same standard deviations? C) Could they be normally distributed? D) Could they be Poisson distributed?