Question

electrical frame manufacturer light bulbs have a life people burns out that is normallydistributed with mean equal to 8 hours and standard deviation uppootti hours find the probability that a bulb burns between 700 and 780 hours
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Answer 1

Answer:

An electrical firm manufactures light bulbs that have a length of life that is approximately normally distributed with a standard deviation of 40 hours. If a sample of 30 bulbs has an average life of 780 hours, find a 96% confidence interval for the population mean of all bulbs produced by this firm.