The lifetime of an insulating material tested accelerated te

The lifetime of an insulating material tested (accelerated testing) at 30kV is known to have a mean of 63 hours and standard deviation of 8 hours. A reliability engineer randomly selects n = 50 specimens and determines their lifetimes. What is the approximate distribution of the sample average of the 40 lifetimes? (Use Central Limit Theorem.) Use the result of part (a) to approximate the probability P( > 65.20). For the following scenarios, describe what the mean mu represents, and set up H0 and Ha related to mu (i.e. What hypotheses would you test to assess the specification/claim/belief?) Do not perform the hypothesis tests. A random sample of 25 pieces of acetate fiber has a sample mean absorbency of 12% with a sample standard deviation of 1.25%. Is there strong evidence that this fiber has a true mean absorbency of less than 20%? A manufacturer of a synthetic fishing line claims that its product has a mean breaking strength of at least 8 kilograms. A random sample of n = 9 fishing line specimens yields a sample average strength of 7.5 kilograms with sample standard deviation of 0.65 sec.

Solution