Article:

Vancouver Police Response Time Twice That of Other Cities

It takes Vancouver police twice as long to respond to an emergency call as most other police forces in North America. Police here take an average of 13 minutes to respond to "priority-one" calls-crimes in progress and serious incidents - compared to 6 minutes in other major cities.

a) Assume that the "priority-one" response time for Vancouver police can be approximated with a Normal model with a mean of 13 minutes and a standard deviation of 3.5 minutes.

i. what proportion of the response times is at least 10 minutes but at most 15 minutes?

ii. what percentage of the response times is at most 8 minutes?

iii. 25% of the response times are longer than how many minutes?

b) Suppose that another "major city" claimed that its police force response times followed a normal model with a mean of 6 minutes. What is the SD of this model if 90% of the response times were at most 10 minutes? Show all steps in your solution.