Question

Consider a product that is "settled in." Its MTBF distribution has been found to be normal with a mean of 10,000 hours and a standard deviation of 100 hours. What is the probability of a breakdown before 8,000 hours? Before 9,000 hours? Would you prefer a policy of preventive maintenance, or a policy of breakdown maintenance, on this product? Explain your choice. Please note that a good logical explanation is critical in this discussion.

Answer 1

Consider the following explanation.

Step-by-step explanation:

Both of the specified times are far below the mean: 8,000 hours is twenty standard deviations away, and 9,000 hours is ten standard deviations away. In both instances, the normal areas table computes the probability of failure to be approximately zero. Most students will opt for preventive maintenance; the standard deviation is quite small compared to the mean, so that preventive maintenance can pretty reliably be used.