Based on 60 readings, the average speed for cars in a main road was 70 kph and coefficient of variation of COV = 0.15. The city council installed a monitoring camera in the road to help regulate this speed. After installation, speed readings of 20 cars were recorded and their mean value became 65 kph and the COV was 0.13. The average daily volume of cars in the road is 3400 cars per day. a) Find 90% confident intervals for the car average speeds before and after camera installation. b) Based on 95% confidence compare the change in the cars average speed before and after installation of the camera. Comment if the speed did in fact change or not because of the camera. c) Estimate a 90% confidence interval for the ratio of the variances between the two situations. Comment if the camera influenced the uniformity of the cars speed. d) If the maximum allowed speed was 80 kph, determine the expected number of violating cars per day before and after camera installation.
Based on 60 readings, the average speed for cars in a main road was 70 kph and coefficient of variation of COV = 0.15. The city council installed a monitoring camera in the road to help regulate this speed. After installation, speed readings of 20 cars were recorded and their mean value became 65 kph and the COV was 0.13. The average daily volume of cars in the road is 3400 cars per day.
a) Find 90% confident intervals for the car average speeds before and after camera installation.
b) Based on 95% confidence compare the change in the cars average speed before and after installation of the camera. Comment if the speed did in fact change or not because of the camera.
c) Estimate a 90% confidence interval for the ratio of the variances between the two situations. Comment if the camera influenced the uniformity of the cars speed.
d) If the maximum allowed speed was 80 kph, determine the expected number of violating cars per day before and after camera installation.
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