Question

The life of light bulbs is distributed normally. The variance of the lifetime is 225 and the mean lifetime of a bulb is 590 hours. Find the probability of a bulb lasting for at most 607 hour
SD = sq rt of 225 = 15

Z = (score-mean)/SD

Look in the back of your statistics textbook for a table called something like “area under normal distribution” to find the proportion/probability related to the Z score.

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