Because the use of CD-ROM and CD-R for storing data has increased considerably, successful retrieving of data from them becomes an important issue for their manufacturers. Eastman Kodak Company was interested in developing Kodak Writable CD and Kodak Photo CD with exceptional data life for CDs stored under different temperatures. To determine level of success in achieving this goal, the company tested a random sample of their product and found the lognormal distribution described the data lifetimes the best (Stinson, Ameli, and Zaino, https:// www.cd-info.com/CDIC/Technology/CD-R/ Media/Kodak.html). They concluded that 95% of the population of Kodak Writable CD Media will have a data lifetime of greater than 217 years under certain conditions.
a Describe this statement using probability density.
b If σ =5, estimate the expected lifetime of Kodak Writable CD Media when used under similar conditions.