The life in hours of a thermocouple used in a furnace is knownto be ap-
proximately normally distributed, with standard deviation
?
= 20 hours. A
random sample of 15 thermocouples resulted in he following data:553, 552,
567, 579, 550, 541, 537, 553, 552, 546, 538, 553, 581, 539,529.
Use the 5 steps in the testing procedure to solve followingquestion:
a) Is there evidence to support the claim that mean life exceeds540 hours?
Use a fixed-level test with
?
= 0
.
05.
b) What is the P-value for this test?
c) Construct a 95% one-sided lower CI on the mean life.
d) Use the CI found above to test the hypothesis.
e) What is the ?-value for this test if the true mean life is560 hours?
