Model

(noun)

A representation of something difficult or impossible to display directly

Related Terms

Examples of Model in the following topics:

  • Economic Models

    • A model is simply a framework that is designed to show complex economic processes.
    • Economists use models in order to study and portray situations.
    • Models are based on theory and follow the rules of deductive logic.
    • However, creating a model does have two basic steps: 1) generate the model, and 2) checking the model for accuracy - also known as diagnostics.
    • Some economic models also use qualitative analysis.

  • Modeling Ecosystem Dynamics

    • Conceptual models describe ecosystem structure, while analytical and simulation models use algorithms to predict ecosystem dynamics.
    • Conceptual models are usually depicted graphically as flow charts.
    • These diagrams are sometimes called compartment models.
    • Like analytical models, simulation models use complex algorithms to predict ecosystem dynamics.
    • These kinds of models tend to be more widely used.

  • Introduction to Model selection

    • The best model is not always the most complicated.
    • In this section we discuss model selection strategies, which will help us eliminate from the model variables that are less important.
    • In this section, and in practice, the model that includes all available explanatory variables is often referred to as the full model.
    • Our goal is to assess whether the full model is the best model.
    • If it isn't, we want to identify a smaller model that is preferable.

  • Essential Functions for Mathematical Modeling

    • The process of developing a mathematical model is termed mathematical modeling.
    • Mathematical models can take many forms, including but not limited to dynamical systems, statistical models, differential equations, or game theoretic models.
    • These and other types of models can overlap, with a given model involving a variety of abstract structures.
    • In general, mathematical models may include logical models, as far as logic is taken as a part of mathematics.
    • For example, a simple model of population growth is the Malthusian growth model.

  • Fama-French Three-Factor Model

    • The Fama–French three-factor model is a linear model designed by Eugene Fama and Kenneth French to describe stock returns.
    • The Fama–French three-factor model is a model designed by Eugene Fama and Kenneth French to describe stock returns .
    • Like CAPM and the Arbitrage Pricing Theory, the Fama-French three-factor model is a linear model that relates structural factors to the expected return of an asset.
    • Unlike those two models, however, the Fama-French model has three specific and defined factors.
    • Though it is more complex than CAPM, the Fama-French model has been shown to be a better at explaining the returns of a diversified portfolio: CAPM explains 70% of returns on average, while the Fama-French model explains 90% on average.

  • Two model selection strategies

    • If one of these smaller models has a higher adjusted R2 than our current model, we pick the smaller model with the largest adjusted R2.
    • That is, we fit the model including just the cond new predictor, then the model including just the stock photo variable, then a model with just duration, and a model with just wheels.
    • Each of the four models (yes, we fit four models!
    • We fit three new models:
    • If one of these models has a larger than the model with no variables, we use this new model.

  • Comparing Nested Models

    • Multilevel models, or nested models, are statistical models of parameters that vary at more than one level.
    • These models can be seen as generalizations of linear models (in particular, linear regression); although, they can also extend to non-linear models.
    • Random intercepts model.
    • Random slopes model.
    • Random intercepts and slopes model.

  • Studying Ecosystem Dynamics

    • Many different models are used to study ecosystem dynamics, including holistic, experimental, conceptual, analytical, and simulation models.
    • A holistic ecosystem model attempts to quantify the composition, interaction, and dynamics of entire ecosystems.
    • A food web is an example of a holistic ecosystem model, which is the most representative of the ecosystem in its natural state.
    • Three basic types of ecosystem modeling are routinely used in research and ecosystem management: conceptual models, analytical models, and simulation models.
    • A simulation model is created using complex computer algorithms to holistically model ecosystems and to predict the effects of environmental disturbances on ecosystem structure and dynamics.

  • Model selection exercises

    • Determine if any other variable(s) should be removed from the model.
    • Determine if any other variable(s) should be removed from the model.
    • Based on this table, which variable should be added to the model first?
    • Based on this table, which variable should be added to the model first?
    • We should consider removing this variable from the model.

  • Web, Network, and Ring of Life Models

    • To more accurately describe the phylogenetic relationships of life, web and ring models have been proposed as updates to tree models.
    • This model is often called the "web of life."
    • However, phylogeneticists remain highly skeptical of this model.
    • In the (a) phylogenetic model proposed by W.
    • Describe the web, network, and ring of life models of phylogenetic trees