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I really need some help with this statistics probability question?

A GE lightbulb is supposed to last for 1,200 hours. In fact, light bulbs of this type last only 1,185 hours with a standard deviation of 70 hours. What is the probability that a sample of 100 lightbulbs will have an average life of at least 1,200 hours?
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Jonathon Rolfson

Feb 20, 2025

The distribution of GE lightbulb lifetimes follows the normal distribution with mean mu = 1185 and standard deviation sigma = 70.0. The lifetime value we’re interested in is x = 1200. The normalized z-score is z = (1200-1185)/70.0 = 0.214285714286and the probability that a GE lightbulb will last longer than 1200 hoursP(X>1200) = P(Z>0.21428571428571427) = 0.4151621288278977 = 1/2.41 that is, only about one in 2.5 GE lightbulbs, or 4 in 10, will last that long.I’m surprised that an actual great corporation would be mentioned in a problem like this.... Show More
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