A machine in a certain factory must be repaired if it produces more than 10% defectives among the large lot of items it produces in a day. A random sample of 100 items from the day's production contains 15 defectives, and the foreman says that the machine must be repaired.
(a) Does the sample evidence support his decision at the 0.01 significance level?
(b) Find a 95% confidence interval for the proportion of defectives produced by this machine.
(c) Find the sample size required to estimate the proportion of defectives within 5%.