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Answer to Question #85311 in Statistics and Probability for Caroline
Question #85311
A batch of 5000 electric lamps has a mean life of 1000 hours and a standard deviation of 75 hours.
Assume a normal distribution.
i) How many lamps will fail before 900 hours?
ii) How many lamps will fail between 950 and 1000 hours?
iii) What proportion of lamps will fail before 925 hours?
iv) Given the same mean life, what would the standard deviation have to be to ensure that no more than 20% of lamps fail before 916 hours
Assume a normal distribution.
i) How many lamps will fail before 900 hours?
ii) How many lamps will fail between 950 and 1000 hours?
iii) What proportion of lamps will fail before 925 hours?
iv) Given the same mean life, what would the standard deviation have to be to ensure that no more than 20% of lamps fail before 916 hours
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Dear ASHISH, please use the panel for submitting new questions.
CFL bulb of a certain make have a mean life of 800 hours with S.d. of 150 hours. Out of 50 thousand bulbs of that make used for street lighting, how many of them would fuse in first 650 hours, if the distribution of the life of bulbs is assumed to be normal? How Many bulbs would be burning after 950 hours?
Another possible answer to part i) is 0.0913. It can be computed with a help of the command =NORM.S.DIST(-1,333;1) in Microsoft Excel.
On answer on question #85311 (i.) how did you go about getting 0.0912
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