Laureysens,et Al

Multiple Choice

Laureysens,et al.(2004) studied the concentration of aluminum in wood from a number of clones of poplar growing in an area with heavy pollution.The same clone was sampled and tested once in August and again in November.The researchers believed that the concentration of aluminum would be shown to be increasing over time and hence higher in November than in August.The following table gives the aluminum concentrations for twelve of the clones. The data are to be analyzed using the Wilcoxon signed rank test.The null hypothesis they established was that the values of aluminum concentrations in the 2 months have the same distribution.What is the value of the statistic W⁺ used for the test of hypotheses?

A) W⁺ = 78
B) W⁺ = 65
C) W⁺ = 5.3
D) W⁺ = 13
E) W⁺ = 63.6