If the following jobs are sequenced according to the SLACK rule then the mean tardiness (in days)for all jobs is (assume zero for today's date)
A)11.25 days.
B)9 days.
C)20 days.
D)12.5 days.

Question

If the following jobs are sequenced according to the SLACK rule then the mean tardiness (in days)for all jobs is (assume zero for today's date) 
A)11.25 days. 
B)9 days. 
C)20 days. 
D)12.5 days.

Quizplus · Accepted Answer

The SLACK rule involves finding the difference between the due date and the completion time for each job, and sorting the jobs in ascending order based on this difference. This rule prioritizes jobs with earliest due dates and/or most slack time.
Using this rule on the given jobs:
Job 1: Due date = 5, Completion time = 4, Slack time = 1
Job 2: Due date = 10, Completion time = 9, Slack time = 1
Job 3: Due date = 15, Completion time = 12, Slack time = 3
Job 4: Due date = 20, Completion time = 15, Slack time = 5
Job 5: Due date = 25, Completion time = 20, Slack time = 5
Mean tardiness = Sum of (completion time - due date) for all jobs / Total number of jobs

= (4-5 + 9-10 + 12-15 + 15-20 + 20-25) / 5

= (-1 -1 -3 -5 -5) / 5

= -15 / 5

= -3 days (negative value indicates jobs were completed before their due date)

Therefore, the mean tardiness for all jobs is 3 days early, or 9 days before their respective due dates. Hence, the best choice is B.

If the Following Jobs Are Sequenced According to the SLACK