Question

(Data from Devore and Peck) Recent studies have looked at the duration of waiting time between a diagnosis and recommendation of surgery until the actual surgery. In the case of potentially lifethreatening conditions, the waiting time on average is hopefully of short duration. For a (assume random) sample of 539 patients recommended for a heart bypass procedure, the sample mean waiting time was 19 days, and the sample standard deviation was 10 days (i.e. x 19,s 10,n  539 ). We will assume the distribution of waiting times is normal with unknown population mean and variance. Z and t Critical values for 90%: z*=1.645, t*(200)=1.653, t*(369.5)=1.649, t*(538)=1.648, t*(739)=1.647 (You will not need all these). Chi-square table (provided).

a. Compute a 90% confidence interval for the population mean waiting time.

b. Compute a 95% confidence interval for the population standard deviation of waiting time, assuming s=10, but changing the sample size to be 26.

c. Compute a 95% lower confidence bound for the population standard deviation of waiting time, again assuming s=10 for a sample size of 26. (3)

Answer 1