Q4. In a reliability test in the company, the time-to-failure values of ten mechanical items of the same design running under identical condition were recorded and are as given in the following table (Q4): Table Q4 Unit No. Time to failure (hours) 1 1800 2 1370 3 1510 4 1230 5 1050 6* 1400 7 2020 8 1630 9* 1700 10* 1300 * Units 6, 9 and 10 had not failed at the end of the test period. Using the median rank method for estimating the failure probability and assuming that the guaranteed life before failure is 500 hours, a) b) c) Calculate and tabulate the median ranks for the data supplied. Plot the cumulative percent failure versus time to failure on the Weibull graph paper supplied. Estimate the shape factor and the characteristic time to failure n for the distribution. Infer from the value of whether the failure is an early failure, a random failure or a wear-out failure.