A Parking Enforcement Officer in Perth is conducting an analysis on the amount of time left on parking

A Parking Enforcement Officer in Perth is conducting an analysis on the amount of time left on parkingmeters in the CBD. A quick survey of 14 metered parking spaces where cars had just left provided the

meters in the CBD. A quick survey of 14 metered parking spaces where cars had just left provided thefollowing times (in minutes).

following times (in minutes).

18

18

17

17

0

0

14

14

4

4

8

8

20

20

17

17

29

29

15

15

29

29

13

13

24

24

34

34

(a) What assumptions must you make to obtain a confidence interval for the mean amount of time left

(a) What assumptions must you make to obtain a confidence interval for the mean amount of time leftfor all vacant meters?

for all vacant meters?

(b) Construct a 95% confidence interval estimate for the mean amount of time left for all vacant

(b) Construct a 95% confidence interval estimate for the mean amount of time left for all vacantmeters.

meters.

(c) Interpret the confidence interval obtained in (b).

(c) Interpret the confidence interval obtained in (b).

(d) The Policy Manager is not totally convinced with the confidence interval estimated in (b), because it is

(d) The Policy Manager is not totally convinced with the confidence interval estimated in (b), because it istoo wide. They would like to be 99% sure that the sample mean is within 3 minutes of the true mean.

too wide. They would like to be 99% sure that the sample mean is within 3 minutes of the true mean.What sample size is required to meet this requirement? Assume the population standard deviation is

What sample size is required to meet this requirement? Assume the population standard deviation isequal to the one identified for the sample of the 14 parking spaces.

equal to the one identified for the sample of the 14 parking spaces.