A GE light bulb is supposed to last for 1200 hours. In fact, light bulbs of this type last only 1185 hours with a standard deviation of 70 hours. What is the probability that a sample of 100 light bulbs will have an average life of at least 1200 hours?
Z is equal to the standardized variable of the average life. In other
words, Z is calculated as follows: the average life minus the sample
mean of the average life and the result is finally divided by the
standard deviation of the average life.
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Z is equal to the standardized variable of the average life. In other words, Z is calculated as follows: the average life minus the sample mean of the average life and the result is finally divided by the standard deviation of the average life.
How do we find what z is?