Specification for a medical device calls for a meanlifetime,  of more than 160 days. The manufacturer isinvestigating whether or not the lifetime of the device meets thisspecification. A random sample of medical devices is selected andtheir estimated lifetime using is measured, with these results (indays): 159.7, 161.9, 164.7, 159.2, 161.3, 161.8, 162.9, 161, 158.5,161.2.
A normal probability plot looks reasonably straight. We will assumethat these lifetimes are normally distributed. Consider asignificance level α=0.05. Â
The critical value is:
