SOLUTION: A manufacturer of light bulbs claims that its light bulbs have a mean life of 693 hours and a standard deviation of 117 hours. You purchased 144 of these bulbs and decided that you

Question 1131398: A manufacturer of light bulbs claims that its light bulbs have a mean life of 693 hours and a standard deviation of 117 hours. You purchased 144 of these bulbs and decided that you would purchase more if the mean life of your current sample exceeded 685 hours. What is the probability that you will not buy again from this manufacturer? Give your answer correct to four decimal places.
Answer by Boreal(15235) (Show Source): You can put this solution on YOUR website!
want z=(x-mean)/sd /sqrt (n)
z<=(685-693)/117/12
z<=-8*12/117 or <=-0.82
probability is 0.2061
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