16.12 Following are the numbers of typographical errors made by two typists over a 20-day period:

Day Typist A Typist B 123456789 10 11 12 13 14 15 16 17 18 19 20 28 35 33 32 41 32 42 32 34 31 29 31 37 35 39 32 25 38 32 34 26 29 30 27 33 35 34 31 28 34 26 25 31 33 33 28 13 37 30 28 Use the signed-rank test at the 0.01 level of significance to determine whether the two typists, on average, make the same number of mistakes against the alternative that Typist A makes more errors than Typist B.