Statistics

An industrial engineer has found that the standard household light bulbs produced by a certain manufacturer have a useful life that is normally distributed with a mean of 250 hours and a variance of 2500.
(a) What is the probability that a randomly selected bulb from this production process will have a useful
life between 190 and 270 hours?
(b) Ninety percent of the bulbs have a useful life in excess of how many hours?
(c) What is the probability that the average life of 10 randomly, independently selected bulbs is less than
240 hours?

asked by bappy
  1. Ffsg

    posted by Anonymous

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