A Buyer for a Manufacturing Plant Suspects That His Primary

A buyer for a manufacturing plant suspects that his primary supplier of raw materials is overcharging. In order to determine if his suspicion is correct, he contacts a second supplier and asks for the prices on various identical materials. He wants to compare these prices with those of his primary supplier. He collected data on 6 different materials from both suppliers. He suspects that the differences are not normally distributed. Which of the following tests will be the most appropriate?

A) Pooled-variance t test
B) Paired t test
C) Wilcoxon rank sum test
D) Wilcoxon signed rank test