Spreadsheet Models for Managers

Getting Access to Spreadsheet Models for Managers

If Spreadsheet Models for Managersyou use Excel to model businesses, business processes, or business transactions, this course will change your life. You’ll learn how to create tools for yourself that will amaze even you. Unrestricted use of this material is available in two ways.

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It resides on your computer, and you can use it anywhere. No need for Internet access.
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If you have access to the Internet whenever you want to view this material, you can purchase on-line access. Unlimited usage. I’m constantly making improvements and you’ll get them as soon as they’re available.

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Order "Spreadsheet Models for Managers, on-line edition, one month" by credit card, for USD 69.95 each, using our secure server, and receive download instructions by return email.
Order "Spreadsheet Models for Managers, on-line edition, three months" by credit card, for USD 199.00 each, using our secure server, and receive download instructions by return email.
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Make your check payable to Chaco Canyon Consulting, for the amount indicated:
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Spreadsheet Models for Managers

Departure characteristics 12/6
Session Links
  • We will assume that the mean service time is constant
  • Distribution of service times
    • Random
      • Statistical distribution
      • If service times are independent we model them as the inter-arrival times of a Poisson Distribution (Exponential Distribution)
  • Departure management
    • As soon as a customer is serviced, they instantly depart
    • Inventory security problem
      • Movie theater: separate doors for exit to prohibit multiple viewings
      • Supermarkets
        • Can’t get out without going through a checkout
        • Must leave after checkout
      • Airline checkin: no place to stand after service

Now that we understand the statistics of arriving customers, let’s look at the departure distribution. The basic difference between these two distributions is that departures depend on arrivals. When the arrival distribution is a Poisson distribution, the statistical distribution that describes their departures is an exponential distribution. It’s the distribution of inter-arrival times of the Poisson distribution. It assumes that customers depart as soon as they’re serviced.

Facilities managers try to manage departures, just as they try to manage arrivals. For example, in supermarkets and in airline check-in areas, there is simply nowhere to stand around after you’ve been serviced. This is a design feature that constrains the customer to leave immediately upon completion of service. Movie theaters actually have special exit doors and crowd control staff to ensure that the theater is emptied as quickly as possible.

Of course, not all managers want to speed up departures — some want to slow them down. For instance, roadside restaurants know that cars (and sometimes tractor-trailers) parked out front are interpreted by prospective customers as endorsements. Speedy service when business is slow is sometimes a counterproductive strategy.

Last Modified: Wednesday, 27-Apr-2016 04:15:26 EDT

The Power of Simplifying Assumptions

Modeling service systems in general is extraordinarily complex, but as we’ve seen, if we make reasonable approximations, we can gain powerful tools that are very easy to apply. In the case of service systems, we assumed that the system was at equilibrium or close to it. Analogously, we can make simplifying assumptions for many other complex questions. Examples are process control, resource scheduling, resource allocation, cost allocation, vehicle routing, and many more.