Southside Hospital in Bay Shore, New York, commonly conducts stress tests to study the heart muscle after a person has a heart attack. Members of the diagnostic imaging department conducted a quality improvement project to try to reduce the turn-around time for stress tests. Turn around time is defined as the time from when the test is ordered and when the radiologist signs off on the test result. Initially, the mean turn around time for a stress test is 68 hours. After incorporating changes into the stress test process, the quality improvement team collected a sample of 50 turn around times. In this turn around time, the mean turn around time was 32 hours, with a standard deviation of 9 hours.
a) Construct a 95% confidence interval for the population mean turn around time.
b) Interpret the interval constructed in (a).
c) Do you think the quality improvement project was a success? Explain.