If the following jobs are sequenced according to the SPT rule then the mean tardiness (in days)for all jobs is (assume zero for today's date)

A)16 days.
B)13 days.
C)5.2 days.
D)3.2 days

Question

If the following jobs are sequenced according to the SPT rule then the mean tardiness (in days)for all jobs is (assume zero for today's date)

A)16 days. 
B)13 days. 
C)5.2 days. 
D)3.2 days

Quizplus · Accepted Answer

SPT (Shortest Processing Time) rule is a scheduling algorithm where the job with the shortest processing time is scheduled first.

Using SPT rule, the sequence of jobs from shortest to longest processing time will be:
Job 3, Job 2, Job 1, Job 4, Job 5

Now, let's calculate the tardiness for each job:
Job 3: Due date - Completion date = 5 - 1 = 4 days
Job 2: Due date - Completion date = 8 - 2 = 6 days
Job 1: Due date - Completion date = 12 - 5 = 7 days
Job 4: Due date - Completion date = 16 - 9 = 7 days
Job 5: Due date - Completion date = 20 - 13 = 7 days

Mean tardiness = (4+6+7+7+7)/5 = 5.2 days

Therefore, the best choice is C.

If the Following Jobs Are Sequenced According to the SPT