The MannWhitney U test is a nonparametric alternative to the student's t test and measures the likelihood that a randomly selected value from sample set 1 will be significantly different from a randomly selected value from sample set 2. When testing for a significant lowering in the value of a parameter in sample set 2, the U test counts the total number of occasions for which any value in set 2 is higher than any value in set 1. The null hypothesis can be rejected if the calculated U value so derived is less than or equal to a test statistic. Use the MannWhitney U test to determine if protein precipitation has significantly reduced the concentration of Mg\" ions in six independent samples of human blood plasma (see the data in Table 1 below and then answer all four questions a} to dill. Table 1 Monti-silica of lift is up'ml In cane-mum of Hg" In u'ml in In human pllll'l'll prior to pmhh human plum after Frat-In prechlhtlm praclpltatlcn