In a reliability test in the company, the time-to failure values of ten mechanical items of the same design running under identical conditions were recorded and are as given in the following table:

Unit No, Time to failure (hours)

1 1432

2 654

3* 1357

4* 737

5 350

6 478

7 1820

8 1056

9 964

10* 561

*units 3,4 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 guarantee life before failure is zero.

Calculate and tabulate the median ranks for the data supplied.