Presentations Annual Meeting are Online!

29th of March 2017
Last week, the annual meeting was a succes. We thank all ±160 attendants for making this meeting a succes!   Read more...

Room 417

22nd of March 2017
The VvS+PR Annual Meeting is held in Room 417 of the Jaarbeurs (Beatrix building).

General Members Meeting Documents online!

12th of March 2017
To see the documents, make sure you have your login information. Please find the documents at: Read more...

Nieuw administratiekantoor

5th of January 2017
Per 1 januari 2017 werkt de vereniging samen met een ander administratiekantoor. Voor vragen of informatie over lidmaatschap, contributie, en andere zaken betreffende de vereniging, graag contact opnemen met:  VvS-OR, Postbus 1058, 3860 BB  NIJKERK, Tel: 033-2473408, e-mail:

Conference of European Statistics Stakeholders - call for abstracts

20th of April 2016
Submit your abstract and participate to the Second Conference of European Statistics Stakeholders, that will be held in Budapest, 20-21, October 2016. Read more...

Werk mee aan internationale normen voor statistische methoden voor Six Sigma, QFD en SPC

18th of December 2015
Voldoet mijn product aan kwaliteitseisen? Hoe kan ik mijn processen efficiënter maken? Sluit mijn product aan bij de wensen van de klant of andere stakeholders?   Read more...

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An Invitation Control Policy for Proactive Service Systems: Balancing Efficiency, Value and Service

When:  18th of May 2017
Starttime  11-12

Galit Yom-Tov (Technion - Israel Institute of Technology)  - An Invitation Control Policy for Proactive Service Systems: Balancing Efficiency, Value and Service Level

Thursday 18 May, 11.00-12.00, Room MF 11-12 (4th floor, MetaForum Building, TU/e)


Proactive service systems permit a controllable arrival rate managed by the service provider, which is different from classic service systems. Conceptually, some (or all) of the customers are invited to the system, so as to allow for a better control over operational indicators and profitability. Such a proactive service system is used, for example, to model an online chat service system, or for planning preventive care strategies for health care service providers.
Through an empirical study of a proactive chat service system, the validity of customer ranking information is elaborated for optimizing invitation control. It is also shown that service level measures can be formulated in terms of penalty for abandonment and cost of waiting. We also discuss the difference between external and internal waiting observed in such systems.

As a result, we develop an infinite-time-horizon multiclass multiserver queueing system with impatient invited customers. We find an asymptotically optimal policy using a fluid approximation, by solving a linear programming problem that maximizes revenues. The asymptotic optimal invitation policy we developed invites customers by their rμ ranking in decreasing order until there are no idle servers. Then, an equivalent threshold policy is proposed that is easy to implement in practice. Numerical simulations were performed to demonstrate the performance of the policy and identify its limitations. We show that the fluid policy has a good performance but is also crude.

In order to refine the fluid policy, we analyzed a fluid approximation of the system under a more flexible threshold policy, that is easily applicable. The equilibrium is found to be asymptotically stable and strongly depend on system parameters, including customers' patience that was previously ignored. Moreover, it depends on the threshold value applied. In order to propose an invitation policy that balances revenues and service level, the probability of implementing admission control is approximated, as well as other performance metrics.

Joint work with Yueming Xie and Liron Yedid-Zion

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10th Conference on Extreme Value Analysis

26th of June 2017 - 30th of June 2017 Read more...

The State of the Art in the Use of Expert Judgement in Risk and Decision Analyses

Ampere Hall, EWI building, TU Delft, Mekelweg 4.
3rd of July 2017 - 5th of July 2017 Read more...

Workshop in honour of Arnold Janssen

21st of July 2017 - 21st of July 2017 Read more...

The tenth Stochastic Activity Month

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