A muffler company advertises that a person will receive a rebate if it takes longer than 30 minutes to replace their muffler. Experience has shown that the time taken to replace a muffler is approximately normally distributed with a mean of 25 minutes and a standard deviation of 2.5minutes. What should the rebate-determining time of 30 minutes be changed to if the company wishes to provide only 0.1% of its customers with rebates?

Question

anonymous · Answer

What are you using to approximate the cumulative normal distribution?