Posted by HELPME on Monday, December 19, 2011 at 9:34pm.
the life of electric bulbs has a normal distribution with a mean of 35 months and a standard deviation of 4 months. What should the warranty period be if the company that manufactures these bulbs does not want to replace more than 2% of the bulbs?
statistics - PsyDAG, Wednesday, December 21, 2011 at 1:47am
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion (.02) and its Z score. Insert the value in the above equation and solve for the score. Remember that the Z score will be negative.
statistics - Ashok Khile, Saturday, January 21, 2012 at 2:36am
Here mean = 35
we have asked that
see normal table
It is z=2.05
remember it is standard normal table value but we have to convert it for x variable for which mean is 35 and s.d. is 4.
do the inverse operation for which we convert x into z.
rounding off it will be 48.
That is answer is 48.
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