Question

1. Parking in Toronto The June 6, 2009 edition of the Toronto Star included an article by investigative reporter Diana Zlomislic in which it was reported that 33 of 100 the 100 parkers that they observed, bumped or mounted the curb while parking. Assume this is a random sample of parkers attempting to park in this area at this time of day. a. Create a 90% confidence interval for the proportion of parkers that will bump or mount the curb. b. Can we conclude that more than 25% of parkers bump or mount the curb? Explain your answer.

Answer 1

a) From standard normal tables, we get for 90% confidence level that:

P( -1.645 < Z < 1.645 ) = 0.9

Now the 90% confidence interval for the population proportion is computed as:

This is the required 90% confidence interval for the proportion of parkers that will bump or mount the curb

b) As the proportion 0.25 lies below the lower bound of the above computed confidence interval, therefore we cannot conclude that more than 25% of parkers bump or mount the curb