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Jets Copies

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Quantitative Methods -MAT 540

JET Copies Case Problem

Assignment #1

Days-to-repair Terri was able to gather data from the college which allowed them to develop a table for the probability distribution of the wait for repair services on JET’s copier. To model the probability of wait times in the JET Copies simulation, the JET partners generated a random number representing the probability of an occurrence of a breakdown. They then programmed a VLOOKUP function to match this breakdown probability to the corresponding “Repair Time in Days” column of the table. The result is the simulated time to get repair service for each breakdown occurrence.

Interval between breakdowns

The James, Ernie, and Terri purchased a copier just like the one used at their college office. When Ernie talked with someone in the dean’s office at State, he was told that the University’s copier broke down frequently often for 1 to 4 days. The partners became worried that their machine would also frequently break down. Although they could not get an exact probability distribution, James was able to determine that breakdowns occurred between 0 and 6 weeks apart. The probability of a breakdown increased as time passed. To model the time between breakdowns in their simulation, JET created a list of random numbers. Next, they applied the probability function f(x) = 2x/a2 0≤ x ≤ a. For this situation, the formula used is x = a √r. Since James estimated breakdowns occur zero to six weeks apart, the formula he used for this simulation is x = 6√r1. He then generated

a list of random numbers and applied the formula to each random number. The result is the simulated time between each breakdown occurrence.

Lost revenue The team estimates that they will sell 2,000 – 8,000 copies per day, at a price of $0.10 per copy. In order to apply this to the simulated breakdown periods, they first generate a distribution of random numbers. The probability function for this element of the simulation is f(x) = 2x/a2 2,000≤ x ≤ 8,000. The corresponding formula is x = 8,000√r3. Applying this formula to each simulated breakdown period gives an estimated number of copies that will not be made due to a breakdown. Next, they multiply the simulated number of foregone copies by the per copy price of 10 cents, and then by the simulated number of repair wait days. This result gives the estimated lost revenue for each simulated breakdown period.

Putting it all together The first element of the simulation is the number of breakdowns that JET’s copier can be expected to experience throughout the 1st year. The pseudorandom numbers generated for this simulation indicate that JET will experience approximately 13 breakdowns over the course of their first year. Additionally, the simulation further estimates that JET will have to wait a total of 31 days over the course of the year to receive repair service on the copier.

The next steps estimating how much revenue JET could potentially lose due to breakdowns. To make this computation the partners first had to simulate how many copies could have been made during the breakdown periods. They could then apply their price of ten cents per copy to arrive at estimated lost revenue for breakdowns. JET’s simulation also includes the cumulative time between breakdowns in weeks, in order to keep track of the one year time period they were modeling.

Conclusion To obtain a reliable average of the annual loss of revenue the company will incur due to the copier breakdown, JET should simulate the breakdown and repair process for a number of years. The partners had decided to produce a simulation for a one year time period estimating the number of potential breakdowns, time period to wait for service calls, and revenue lost due to machine downtime. If the potential lost revenue equaled or exceeded $12,000, they would purchase a smaller machine to serve as backup while the larger, more expensive model was being repaired. The simulation estimates that JET could lose almost $19,500 in revenue over a year. Since this amount exceeds the $12,000 they decided on, they should proceed with their plan to purchase the backup copier. Although the upper and lower confidence levels indicate 95% confidence that the average lost revenue is a good estimate, there are several limitations to the model. First, the simulation covers a short period of time for this type of model. The partners did agreed however, to program the simulation for one year and base their decision on this

analysis. The simulation is further limited because JET was unable to gather enough information to establish specific probabilities for the different variables. Finally, the partners should have conducted a thorough simulation to gather this needed information before that they purchasing the first copier and started the business. But since they already purchased the first copier, they definitely need to purchase the back-up copier to ensure that they do not have $19,000 of loss revenue in their first year.

Resources

Taylor, B. M. (2010). MAT540: Quantitative methods: 2010 custom edition. Upper Saddle River, NJ: Pearson/Prentice Hall.

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