hours with no more failures. In other words, this was a time-terminated 5000 hour test with 4failures. For a time-terminated test with four (4) failures, how many degrees of freedom (v) does this represent? Using Chi-Squared, calculate the lower confidence level MTBF for a 60% confidence level (40% risk factor) for this test. The same test was continued to 7631 hours (2631 additional hours) with no additional failures. Using Chi-Squared, calculate the lower confidence level MTBF for a 90% confidence level (10% risk factor) for this test. Compare your two MTBF answers, and comment on how this illustrates a way of increasing the confidence level of a test from 60% to 90%
Fig: 1