Twenty-five units were tested until 15 failures were generated. The following failure times, in…

Twenty-five units were tested until 15 failures were
generated. The following failure times, in hours, were observed:

52 65 66 70 71 73 78 79 80 81 83 93 94 99 100

Compute a two-sided 90 percent confidence interval for the
MTTF and the guarantee lifetime for the two-parameter exponential distribution.
Estimate the design life if specifications call for a 95 percent reliability.