Question

Specification for a medical device calls for a mean lifetime,  of more than 160 days. The manufacturer is investigating whether or not the lifetime of the device meets this specification. A random sample of medical devices is selected and their estimated lifetime using is measured, with these results (in days): 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 assume that these lifetimes are normally distributed. Consider a significance level α=0.05.  

The critical value is:

Answer 1

Solution-

Test results that the null hypothesis is rejected.

So ,there is enough evidence to claim that Specification for a medical device calls for a mean lifetime is more than 160 days