the incubation period of ebola virus is known to have a normal distribution with a mean of 10 days and a standard deviation of 7 days suppose a group of researchers claimed that the true mean is shorter than 10 days. a test is conducted using a random sample of 23 patients. consider a rejection region suppose the test failed to reject . if the true mean incubation period is 6 days, what is the type ii error probability of the test using (round off to third decimal place)?