11-1. Consider the spot speed data below, collected at a rural highway site under conditions of uncongested flow: Number of Vehicles Speed Group Observed (mi/h) (N) 15-20 0 20-25 love 4 25-30 9 30-35 to odma 18 35-40 35 40-45 42 45-50 32 50-55 20 55-60 9 60-65 0 (a) Plot the frequency and cumulative frequency curves for this data. (b) Determine the median speed, the modal speed, the pace, and the percentage of vehi- cles in the pact from the curves, and show how each was found. (c) Compute the mean and standard deviation of the speed distribution. V (d) What are the confidence bounds of the estimate of the true mean speed of the distribution with 95% confidence? With 99.7% confidence? (e) Based on the results of this study, a second is to be conducted to achieve a tolerance of ±0.8 mi/h with 95% confidence. What sample size is required? (f) Can these data be adequately described as "normal"?