There is a large supply of light bulbs with the average life of 1000 hours and the standard deviation of 50 hours. A light bulb is drawn at random. Find the probability that it will last more than 1020 hours. A random sample of 25 light bulbs is drawn. Find the probability that the sample average life is more than 1020 hours.
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!
There is a large supply of light bulbs with the average life of 1000 hours and the standard deviation of 50 hours.
- A light bulb is drawn at random. Find the
probability that it will last more than 1020 hours. - A random sample of 25 light bulbs is drawn. Find the probability that the sample average life is more than 1020 hours.
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