Question: Heavy duty epoxy glue is produced by a process with failure strength of test samples approximated by a Normal distribution with a standard deviation of 100 pounds. Let’s consider the product designated as ‘4000 pounds strength’.

a) If the manufacturing process is targeted at a mean failure strength of 4000 pounds, compute the central range [‘two-tailed’] which will include with 90% probability the strength of a specific test sample.

b) For this same target mean strength of 4000 pounds, compute the minimum test failure strength which can be assured with 90% probability.

c) If the manufacturer desires to assure a 99% probability that the strength is at least the designated 4000 pounds, where must the manufacturing target mean strength be set?