4. The data below are the final grades of the students of two teachers of the same course. Is there evidence that Teacher A is a tougher grader than Teacher B? (a) Report an appropriate nonparametric test with a 2% significance level. Write out the full procedure taught in this class. (b) If we were making an error here, which type would it be? Write out in words, in context, what making such an error would mean. (c) Explain the power of the test in words, in context