Task 2: DES Model

QN, a broadband provider, runs a call center to handle telephone calls. When customers call, the call is immediately picked up by a recorded message which says:

‘Welcome to the QN sales and help line. After the tone, press (1) for sales enquiries, press (2) for account services, press (3) for technical enquiries, press (4) for all other enquires or press (5) to repeat this menu’.

If the customer presses numbers 1 to 4 on their handset they are then directed to the correct line where they await their call to be answered. If they press 5, the recorded message immediately repeats itself. Data shows that 20% of callers press ‘1’ , 15% press ‘2’, 20% press ‘3’, 40% press ‘4’ and 5% press ‘5’. It has been found that once a customer has chosen the correct enquiry line, s/he will only wait for a maximum of 10 minutes before hanging up if the call is not dealt with.

It has been found that 50% of ‘all other enquiries’ are in fact casual enquiries from prospective ‘new’ customers and such calls are redirected to sales. The other 50% of ‘all other enquiries’ are redirected to ‘technical enquiries’. As such, staff working on the ‘all other’ line do their job in two parts: first they must determine what type of call it is. Secondly, they must redirect the call correctly.

Historical ‘sales’ records show that 1 in 10 of ‘new’ customers take up a subscription immediately. In such circumstances, on finishing the ‘sales’ call, the new customer is redirected by the sales staff to the technical enquiries where the ‘tech’ staff can discuss the details of setting up a new broadband account with the new customer.

Re-directing a call on any line takes no time at all. Redirected customers do not take priority over other customers already in the queue.

The call center opens at 2 pm and closes at 10 pm, Monday to Saturday; and it is operated by eight staff in total. Two members of staff are ‘techs’ dedicated to dealing with ‘technical’ enquiries only. The other six are ‘general’ and have the training and equipment to deal with all other types of enquiries, i.e. the ‘sales’, ‘accounts’ and ‘all other’, although each member of staff can only deal with one enquiry at a time. During a shift the ‘staff’ are divided into teams of two with each team being dedicated to a particular enquiry line for the entire shift.

On average the call center receives a call every three minutes and the calls are random, i.e. they are exponentially distributed.

Data collected over time shows the time it takes to deal with a ‘sales’ enquiry is distributed as follows.

Time to complete sales call (minutes)         Number observed

Under 20                                                                 163

20 to under 30                                                         17

30 to under 60                                                         20

Dealing with other enquiries takes staff the time indicated by the fitted probability distributions in the table below:

Create a simul8 model of this system and simulate the call centre. This is your baseline model.

The management of QN is concerned by the number of dropped calls, i.e. customers that hang up before the call is picked up. They suppose that the number of dropped calls can be reduced if the current members of staff were used more creatively. Can this be done? Experiment with your model.

Write a report detailing the what-if-scenarios you have tried, the results you have obtained, your recommendations to the management of QN and a discussion of what the recommendations might imply in practice.

Your report should be a professional-looking document aimed at lay people who have no expert knowledge of Discrete Event Simulation.

Save the final simul8 model showing the changes you have recommended. This is your final model.

Model Submission:

In case we need to check your models, you must submit two Simul8 files: the first should be a base model of the system as it is now. The second should be your final model including the changes that you wish to recommend. Name both using your student number as suffix, for example, as Baseline_123456.s8 and Final_123456.s8.