SOLUTION: The lifetimes of light bulbs of a particular type are normally distributed with a mean of 360 hours and a variance of 25 hours. What percentage of the bulbs have lifetimes that is
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Question 1086128: The lifetimes of light bulbs of a particular type are normally distributed with a mean of 360 hours and a variance of 25 hours. What percentage of the bulbs have lifetimes that is in between 355 hours and 365 hours? Answer by Boreal(15235) (Show Source):
You can put this solution on YOUR website! Want the z scores of each
z=(x-mean)/sd
at 355 hours, z=(355-360)/5; the variance is 25, the standard deviation is sqrt (V)=5. z=-5/5=-1
at 365 hours, z=(365-360)/5=+1
Probability of z between -1 and 1 is 0.6827
