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Office of Health Assessment and Epidemiology
Policy Analysis Unit
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Policy Analysis Unit


Contact Information
Policy Analysis Unit
Office of Health Assessment and Epidemiology
Los Angeles County Department of Public Health

313 N. Figueroa St., Room 127
Los Angeles, CA 90012
Phone: (213) 240-7785
Fax: (213) 250-2594
Email: pau@ph.lacounty.gov
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Model Simulation

What is Model Simulation?

A simulation model is a simplified mathematical, logical, or other structured representation of a system that approximates the real system. Models are simpler than the system they represent but should incorporate most of its relevant features. Models are created with data, equations, and computations to imitate the behavior of the system. A key advantage of working with models is that they can be reconfigured and experimented with, while this could be expensive, time-prohibitive, impractical, or unethical to do in the actual system.

A central purpose of a model is to enable users to predict how changes to the system will affect its outputs. In public health, a model can be a useful tool to complement traditional public health methods in policy planning, assessment, and evaluation. For instance, evaluation of the data collected by public health programs result in estimates of short-term impacts on the individuals and institutions directly targeted by these programs. Simulation models can complement these analyses by combining the results from the short-term evaluations with data and evidence from existing studies to project long-term outcomes and for a wider population.

Simulation models could also generate projections of outcomes under a variety of scenarios by combining interventions, changing time frames of the intervention, or targeting different populations. For example, a model could help compare the impact an intervention would have if it targeted only underserved populations or the entire population of Los Angeles.  Additionally, simulation models can be designed to capture the competing risks that may arise from interventions or policy changes, so that policymakers have a more realistic estimate of the impact of the interventions by taking into account the trade-offs between the costs and benefits of the various alternatives.

What are the basic components of a Model?

While different modeling methods have different basic components, all simulation models have inputs, outputs, and the model itself.

inputs/outputs image

As an example, below we show the inputs and outputs in the Future Los Angeles simulation model, one of our current modeling projects, which will provide long-term projections of health and economic outcomes for the population of Los Angeles County (LAC). Flow chart of inputs/outputs of a simulation model 

Another example is shown below. This diagram represents the transitions over time between four health states (uninfected, latent TB infection, TB disease, and death). This model was used to estimate the health and economic impact of four alternative policies to screen school-aged children in Los Angeles County for Tuberculosis. Diagram of 4 health states of TB infection 

Where can I learn more about simulation modeling?

For more information about where you can learn more about simulation modeling , see External Resources page.

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