The mean life of a certain computer hard disk in continual use is 6 years. (a) H

Question

The mean life of a certain computer hard disk in continual use is 6 years. (a) How long a warranty should be offered if the vendor wants to ensure that not more than 10 percent of the hard disks will fail within the warranty period? (Round your intermediate values to 4 decimal places and final answer to 4 decimal places.) Period of warranty years (b) How long a warranty should be offered if the vendor wants to ensure that not more than 25 percent of the hard disks will fail within the warranty period? (Round your intermediate values to 4 decimal places and final answer to 4 decimal places.) Period of warranty years

Explanation / Answer

lambda = 6
using poisson approximation to normal, we get
mean = 6
std.dev. = sqrt(6) = 2.4495

a)
For 25%, z-value = 1.281551566
xbar = mean + z*sigma
xbar = 6 + 1.281551566*2.4495
xbar = 9.1391

Hence warranty periond should be 9.1391 years

b)
For 25%, z-value = 0.67448975
xbar = mean + z*sigma
xbar = 6 + 0.67448975*2.4495
xbar = 7.652155725

Hence warranty periond should be 7.6522 years

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