Test the proportion of customers favouring underground installation is more than 60%.
A telephone company is trying to decide whether some new lines in a large community should be installed underground. Since a small surcharge would be added to the phone bills to pay for the extra installation costs the company has decided to survey customers and proceed only if the survey strongly indicates that more than 60 percent of all customers favour underground installation. In a random sample of 160 customers, 115 favour underground installation in spite of the surcharge.
-Construct a 99 percent confidence interval for the proportion of customers favouring underground installation.