a. What is the probability that the hair dryer will be in working condition for more than 5 years?
b. What is the minimum and maximum life expectancy of the middle 90% of hte hair dryers?
m = 4, s = 8/12 = 2/3
(a) x = 5
z = (x - m)/s = (5 - 4)/(2/3) = 1.5
P(x > 5 years) ...
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