Critical Ratio

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    Critical Ratio(CR)

        Critical Ratio is an index number computed by dividing the time remaining until due
    date by the work time remaining. As opposed to priority rules, critical ratio is dynamic and
    easily updated. It tends to perform better than FCFS, EDD, SPT, and LPT on the average
    job lateness(delays) criterion. The critical ratio gives priority to jobs that must be done to
    keep shipping on schedule. It is used in conjuction with MRP systems and has broad
    industrial application. The critical ratio is measure of urgency of any order compared to the
    other orders for the same facility. The ratio is based on when the completed order is
    required and how much time is required to complete.

            The step for using this rule are:

At the starting program, user input the numbers of job, the jobs name, the works day remaining and the due date of each job and as well the today's date.
The today's date and the number of job are just inputted once time. Then, the others are followed the value of the number of jobs inputted.
After that, compute the critical ratio by using the formula.
The formula for Critical Ratio is:
                    CR = time remaining / works day remaining
After calculating the CR for each job, give the priority order by using the value of the calculated critical ratio. The priority order is performed from smaller to larger.
There are 3 characteristics can be seen from the critical ratio:

paw_gr.gif (128 bytes)    A job with low critical ratio(less than 1.0) ---- falling behind schedule.
paw_gr.gif (128 bytes)    If  CR is exactly 1.0 ---- the job is on schedule.
paw_gr.gif (128 bytes)    If CR is greater than 1.0 ---- the job is ahead of schedule and has some slack.

            The critical ratio help in most production scheduling system as below:
Determine the status of specific job.
Establish relative priority among jobs on a common basis.
Relate both stock and make-to-order jobs on a common basis.
Adjust priorities( and revise schedules) automatically for changes in both demand and job progress.
Dynamically track job progress and location.

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

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