An inspector are measured the diameter of a ball bearing using a new type of caliper. The results were as follows (in mm): 0.265, 0.263, 0.266, 0.267, 0.267, 0.265, 0.267,0.267, 0.265, 0.268, 0.268, and 0.263.

(a) Use the Wilcoxon signed-rank test to evaluate the claim that the mean ball diameter is 0.265 mm. Use α = 0.05.

(b) Use the normal approximation for the test. With α = 0.05, what conclusions can you draw?