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.
the life span of a calculator manufactured by the intel corporation has a normal distribution with a mean of 54 months and a standard deviation of 8 months. The company gurantees that any calculator that start malfunctioning within 36 months of the purchase will be replaced by a new one. What is the probability that a randomly calculator will be replaced by a new one?
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