Summary and Comments
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Summary of Result:

The results of these four rules are summarised below:

Rule Average Completion Time(days) Utilisation (%) Average no. of Jobs Average Delays(days)
FCFS 15.4 36.4 2.75 2.2
EDD 13.6 41.2 2.42 1.2
SPT 13.0 43.1 2.32 1.8
LPT 20.6 28.2 3.68 9.6

Comments on the Result:

            As in the Example, LPT is the least effective measurement of sequencing for the company. SPT is superior in three measures and EDD in the fourth(average delays). This is typically in the real world also and has been supported by a
number of simulation experiments. Actually, no one sequencing rule always excels on all criteria. Some experience indicates that:

Shortest processing time is generally the best technique for minimising job flow and minimising the average number of jobs in the system. Its chief disadvantage is that long-duration jobs may be continuously pushed back in priority in favor of short-duration jobs. Customers may view this dimly, and a periodic adjustment for longer jobs has been made.
First come first serve does not score well on most criteria( but neither does it score particularly poorly). It has the advantage, however, of appearing fair to customers, which is important in service systems.

 

Example with Demo Solution by using Critical Ratio   Example with Critical Ratio Method

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[Example with Demo Solution 1 by using Priority Rules]