The lifetime distributions of high-speed recordable optical disks is assumed to follow lognormal distribution (Irine and Okino, IEEE Trans. on Magnetics, 2007). Suppose μ = 2.5 and σ = 0.5 weeks.
a Compute the mean and variance of this distribution.
b What percent of optical disks are expected to last over 20 weeks?
c If 98% of disks fail before a0 weeks, then determine the value of a0.