SOLUTION: the lifetimes of a brand of electric light bulbs are normally distributed with mean 1300hours and standartd deviation 120hours. a light bulb is selected at random and tested by ke
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Question 1067247: the lifetimes of a brand of electric light bulbs are normally distributed with mean 1300hours and standartd deviation 120hours. a light bulb is selected at random and tested by keeping it on continuously
find the probability that it has a lifetime of over 1540hours?
its has a lifetime between 1222 and 1540 hours?
two light bulbs are selected at random.
find the probability that they both last between 1222 and 1540
You can put this solution on YOUR website! z=(x-mean)/sd
=(1540-300/120=2
probability z>2=0.0228
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(1222-1300)/120=-78/120=-0.65
probability -0.65
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That would be the probability just obtained squared, since they are independent: 0.5175 if I don't round the last one.
