Σ Using the data furnished in Problem 4-9, draw the histogram frequency distribution and cumulative percentage distribution for each set of data and determine (a) average speed, (b) 85th-percentile speed, (c) 15th-percentile speed, (d) mode, (e) median, and (f) pace. Problem 4-9: The accompanying data show spot speeds collected at a section of highway located in a residential area before and after an increase in speed enforcement activities. Using the student's t test, determine whether there was a statistically significant difference in the average speeds at a significance level of a = 0.05 (the 95 percent confidence level). Also report, for both the before and after cases, the mean speed, standard deviation, 85th percentile speed, and percentage of traffic exceeding the posted speed limit of 30 mi/h. Before After Before After 40 38 37 433333 23 38 25 35 33 35 25 30 36 30 37 38 30 34 39 23832 21 35 30 33 21 Before After Before After 28 23 35 28 35 28 36 23 35 24 34 24 40 31 33 27 33 24 31 20 35 20 36 20 36 21 35 30 36 28 33 32 40 35 39 33 Using the data furnished in Problem 4-9, draw the histogram frequency distribution and cumulative percentage distribution for each set of data and determine (a) average speed, (b) 85th-percentile speed, (c) 15th-percentile speed, (d) mode, (e) median, and (f) pace.