IF YOU ANSWER THIS QUESTION, ANSWER STEPS 1, 2, 3 AND 4 AND SHOW THE STEP-BY-STEP METHOD!!!

The times to failure of ten mechanical units of the same design running under identical condition are given in the following table:

Unit No	Time to failure (hours)
1	1300
2	870
3	1010
4	730
5	550
6*	900
7	1520
8	1130
9*	1200
10*	800

* Units 6, 9 and 10 had not failed at the end of the test period.

IF YOU ANSWER THIS QUESTION, ANSWER STEPS 1, 2, 3 AND 4 AND SHOW THE STEP-BY-STEP METHOD!!!

Using the median rank method and assuming that the guaranteed time before failure is zero,

1) Calculate and tabulate the median ranks for the data supplied.

2) Plot the cumulative per cent failure versus time to failure on the Weibull graph paper supplied. (Remember to secure the graph paper to your answer book.)

3) Estimate the shape factor and the characteristic time to failure for the distribution. Infer from the value of whether the failure is an early failure, a random failure or a wear-out failure.

4) Estimate the reliability of the unit at 900 hours, its failure probability between 900 and 1000 hours, and the probability that the unit that is running at 900 hours will fail before reaching 1000 hours.