The influence chart is used as a visual representation to aid in the comprehension of critical inputs, outputs and relationships of a given problem and is helpful in the early stages of modeling. The chart uses simple flowchart like symbols to annotate the different concepts for each step in the chart. For example the objective or outcome is indicated by a hexagon, circles indicate miscellaneous variables, an upside down triangle is a determining or input variable, the box is used to depict a decision variable, and lastly the random variables are enclosed in a double circle. The relationships between these symbols are identified with arrows from the determining variables (the variable that must be calculated) to the outcome variable, the result of the calculation. Other modeling decisions to understand and consider when developing them for a model or reviewing them is that a variable is a fixed or known quantity if it has no input variables. When developing the influence chart, the modeler should begin with the outcome first, followed by the determinants for the outcome, continue with determining factors, add input and decisions, and always use consistent symbols for the variables. Ultimately, influence charts should be as simple as possible and should aid the modeler in making the initial description of their intended model while still being flexible enough to handle the numerous modifications that occur as the modeling process evolves.(Powell & Baker, 2009)
References:
Powell, S. G., & Baker, K. R. (2009). Management Science, The Art of Modeling with Spreadsheets. Hoboken, NJ: Elbe, Susan.
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