ISE 885

1. Formulation Problem Area Problem Model Translation Implementation Analysis/Solution ISE 885

2. ISE 885 I. TYPES OF MODELS A. Iconic Models: Physical Representations of an Item 1. Examples: Doll, Plastic model car, ship, plane, wind tunnel test model, photograph, etc. 2. Disadvantages: Difficult to make changes to determine effect. Cannot represent abstract relationships. B. Analogue Models: More abstract graphical representations. 1. Examples: Demand curves, frequency diagrams, flow charts, Pert networks 2. Disadvantages: Difficult to optimize, but generally easy to identify ways of making small improvements. C. Mathematical Models (Symbolic); 1.Quantitative – Qualitative 2.General – Specific 3.Probabilistic – Deterministic 4.Descriptive – Optimizing 5.Static - Dynamic

3. ISE 885 II. LIST OF SOME STANDARD MODEL TYPES Decision Theory Models Sequencing Models Allocation Models Assignment Models Competition Models Replacement Models Inventory Models Queuing Models Simulation Dynamic Programming Models Routing Models Heuristic Models Behavioral Models

4. ISE 885 IV. UPDATED SCIENTIFIC METHOD A. Observation B. Definition of Real Problem C. Construction of the Model 1. Itemize all components that might be relevant to the effectiveness of the system. 2.Experiment if possible or obtain existing data and through data analysis determine which components will be represented in your model. 3.Combine and/or divide some components. 4.Determine which are fixed and which are variable (uncontrollable or controllable). 5.Assign a symbol to each element. 6.Construct equation, functions, inequalities, etc. to model the interrelationships among components. D. Exercising the Model (Optimizing and/or Simulating) 1.Development of Alternative Solutions   2.Selection of Opt. Solution through experimentation   3.Economic Analysis   E. Implementation

5. ISE 885 THE BASIC INVESTIGATIVE PROCESS IN OPERATIONS RESEARCH (Adapted from Saaty, Ackoff, Hurni, and others) The following detailed outline of the procedures followed in Operations Research is an idealized interpretation and should not be construed as a cookbook view on "how to do O.R.". To some extent all of these procedures are found in any systematic approach to problem solving at the systems or operations level. In any specific situation, however, the attention of the research team may be directed to just a few of these procedures. In fact, for certain problems, steps 1-9 have already been spelled out for the research team. In other cases implementation is not desired for the time being. Often university groups or research groups such as Rand assume a given type of operational problem, the existence of certain kinds of data and certain constraints or solutions and concentrate on the development of more explicit, analytical models which will be useful over a wide variety of situations. Thus, the suggested O.R. process need not be (indeed it is not) the sole criterion on which a given study is adjudged to be operations research.

6. ISE 885 I. Planning (Judgment) Phase 1. Description of the operational functions involved (essential for team orientation) 2. Establish operational symptoms 3. Establish management objectives 4. Establish time and dollar constraints to the proposed research activity 5. Establish the degree of accuracy required in the results 6. Isolate the processes and variables pertinent to the problem 7. Determine measure(s) of operational effectiveness 8. Establish the type and range of decision variables applicable to the problem. 9. Formulate the problem relative to factors involved, range of decision variables and management objectives

7. ISE 885 II. The Research Phase 1. Initial observation - data collection 2. Determine units of measurement 3. Hypothesis formulation 4. Construction and development of a model which symbolizes the problem defined. 5. Specify model assumptions and constraints 6. Establish methods for collection of data required in the model 7. Manipulation of the model, sensitivity analysis, interpretation and prediction 8. Verification (testing) of the model with observation of the ongoing operation and tests for model assumptions and sensitivity of solutions. 9. Successive model enrichment and refinement (sometimes by lack of data) by repeat of prior steps (note retracting to any step above is possible).

8. Model 1 Model 2 Model 3 Evaluation: No-Good Evaluation: No-Good Evaluation: OK Data New Data New Data New Data ISE 885 V. MODEL DEVELOPMENT ALGORITHM Symbolic World Business (Real) World

9. ISE 885 • Implementation Phase • 1. Establishing methods for management use of the model • 2. Establishing controls over data inputs to the model • 3. Interpretations of model solutions into recommended actions(decision) for management.

10. ISE 885 III. FOUR COMMANDMENTS FOR OR OR is a team effort with team members having varied backgrounds OR teams examine functional relationships for a systems overview in order to define the problem, its boundaries, and the interfacing across the boundaries. OR teams apply the updated scientific method as a planned approach to problem solving. OR teams uncover new problems for study.

11. ISE 885 FRUSTRATIONS AND DIFFICULTIES ENCOUNTERED IN THE STUDY 1. Research time extremely limited in A. Total time and B. Time allowed for presentation 2. Difficulty in communication between the A. Researchers themselves B. Researchers and Professor C. Researchers and Sponsor D. Researchers and Fellow Students 3. Lack of Data 4. Publications give models only for the "nice" problems or are highly specialized and not appropriate to one current problem.

12. ISE 885 FRUSTRATIONS AND DIFFICULTIES ENCOUNTERED IN THE STUDY 5. Disagreements between researchers in A. Philosophical questions regarding study B. Objectives in what they want to get out of the study C. Technical considerations (models, constraints, etc.) D. Emphasis E. Approaches to the study 6. Necessity to make assumptions and simplifications that depart (minimally we hope) from reality. 7. Inability to implement and have the satisfaction of seeing the solution in successful use. 8. Lack of detailed and complete knowledge in every field that might be useful to the study, (i.e.. Economics, Psychology, Philosophy, etc.) and not sufficient time to gain this knowledge. 9. That "nagging feeling" that perhaps you could have done better with more time and effort. 10. That the week has only 168 hours, considering the enormous size of the problem.

13. ISE 885 REASONS FOR FAILURE OF OR STUDIES 1. Reorganization of the company, which changes the persons responsible for the operations under study. 2. Lack of involvement of a high enough level of management to enforce interdepartmental coordination. 3. Attempts by individuals to capture the research so that it can be used to serve some personal, rather than organizational objectives. 4. Economic pressures that lead to a general reduction of expenditures for outside services. Ackoff, Russell L., "Unsuccessful Case Studies and Why," Operations Research, Vol. 8, 1960, p. 259

14. ISE 885 WAYS OF AVOIDING FAILURE 1. Do not ever sign a contract you cannot break. 2. Never report to anyone lower than the authority capable of controlling all the functions involved in a study. 3. Never report to the responsible authorities through intermediaries. 4. Never fail to complain forcibly to management about undesirable research conditions. 5. Never perform research for anyone at no cost to him. Ackoff, Russell L., "Unsuccessful Case Studies and Why," Operations Research, Vol. 8, 1960, p. 259