The average life span of one particular brand of refrigerator is 12 years with a standard deviation of 0.8. Find the percentage of the refigerators that last between 10 and 14.5 years. O 99.3% 99.9% 95.9% 97.8%

Suppose that the speeds of cars travelling on California freeways are normally distributed with a mean of 63 0 miles hour miles tickets for cars with speeds exceeding 80 . The records show that exactly 5% of the speeds exceed this limit. Find the standard deviation of the speeds of cars travelling on California freeways. Carry your intermediate computations to at least four decimal places. Round your answer to at least one decimal place. hour miles hour The highway patrol's policy is to issue

A manufacturer knows that their items have a normally distributed lifespan, with a mean of 2.7 years, and standard deviation of 0.9 years. The 3% of items with the shortest lifespan will last less than how many years? Give your answer to one decimal place. years

construct a 90% condifence interval for the population mean of total calcium in this patient blood