1.
Compute the critical z value for the given confidence
level.
a) 90% confidence level, the critical z value is: z
=
b) 96% confidence level, the critical z value is: z
=
2.
Paint Manufacturing: A paint
manufacturer is developing a new type of paint. Thirty panels
were exposed to various corrosive conditions to measure the
protective ability of the paint. The mean life for the
samples was 168 hours before corrosive failure. The life of
paint samples is assumed to be normally distributed with a
population standard deviation of 30 hours.
Questions:
a) Find the 95% confidence interval for the population
mean life of this paint. Identify the calculator function
that you are using and write the answer in the
format: l o w e r b o u n d a r y < μ < u p p e r b o u n d a r y
b) Interpret your confidence interval in the context of the
problem.
c) Compute the margin of error in part A.
d) How many panels must be tested and exposed to various
corrosive conditions to be 99% sure that the sample mean life of
the paint samples is within 5 hours of the true mean
life? Show your work or explain how
you obtained your answer.