Both a gravimetric and a spectrophotometric method are under consideration for determini...

Both a gravimetric and a spectrophotometric method are under consideration for determining phosphate content of a particular material. Twelve samples of the material are obtained, each is split in half, and a determination is made on each half using one of the two methods, resulting in the following data:

Use the Wilcoxon test to decide whether one technique gives on average a different value than the other technique for this type of material.