Question

Over a 2 week period a study of junction failures was conducted. The junctions exposed to heat cycling repeatedly until they failed. Five test stations were in place and failed units were replaced immediately during test. The tests ended at a predetermined time. The data below are failure times in hours. The values marked with an asterisk (*) are censored. Utilizing Spreadsheet to compute values and make plots.

     23, 278* , 73, 263*, 156*, 33, 22*, 72, 91, 32, 102, 81*, 115, 121, 105*, 263, 74, 53*

1.  Calculate the maximum-likelihood estimate of the mean lifetime, assuming the lifetimes are exponentially-distributed.

2. Calculate 95 percent two sided confidence interval for the true mean lifetime, assuming the lifetimes have an exponential distribution.

Answer 1