Problem: The life of a watch battery is normally distributed with a mean of 1,000 days and a standard deviation of 60 days.
Q1. What fraction of the batteries is expected to survive beyond 1100 days?
Q2. What fraction will survive fewer than 880 days?
Q3. Sketch the reliability function
Q4. What length of warranty is needed so that no more than 10% of the batteries will be expected to fail during the warranty period?