The average lifetime of smoke detectors that a company manufactures is 60 months, and the standard deviation is 8 months. Average lifetime is normally distributed. Find the probability that a random sample of 29 smoke detectors will have a mean lifetime between 57 and 64 months. Round the final answer to at least four decimal places and intermediate z – value calculations to 2 decimal places.
Continuous Probability Distributions
Probability distributions are of two types, which are continuous probability distributions and discrete probability distributions. A continuous probability distribution contains an infinite number of values. For example, if time is infinite: you could count from 0 to a trillion seconds, billion seconds, so on indefinitely. A discrete probability distribution consists of only a countable set of possible values.
Normal Distribution
Suppose we had to design a bathroom weighing scale, how would we decide what should be the range of the weighing machine? Would we take the highest recorded human weight in history and use that as the upper limit for our weighing scale? This may not be a great idea as the sensitivity of the scale would get reduced if the range is too large. At the same time, if we keep the upper limit too low, it may not be usable for a large percentage of the population!
The average lifetime of smoke detectors that a company manufactures is 60 months, and the standard deviation is 8 months. Average lifetime is
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