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Teaching Systems Thinking in Spreadsheets. Mohammad Mojtahedzadeh Attune Group, Inc Deborah Upton Stonehill College. Modeling Spectrum:. Exposé. System Dynamics. Spreadsheet. Simple Manipulation. Complex Formulation. Build on Simple manipulation to arrive at Complex formulation.
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Teaching Systems Thinking in Spreadsheets Mohammad Mojtahedzadeh Attune Group, Inc Deborah Upton Stonehill College
Modeling Spectrum: Exposé System Dynamics Spreadsheet Simple Manipulation Complex Formulation Build on Simple manipulation to arrive at Complex formulation
Exposé Modeling Spectrum: System Dynamics Simple Manipulation Complex Formulation • Hidden relationships • Visualization of structure Spreadsheet • Local in time and space • Global in time and space • One way linkages • Circular Causality • Stock-and-Flow • Mathematical Nonlinearity • Data-Point Nonlinearity
Hidden relationships: The Spreadsheet Approach:
Hidden relationships The Spreadsheet Approach: Makes it difficult to understand, analyze and, communicate…
Exposé in MS Excel: Tree Diagrams of Precedence make the connections among the CELLS visible
Local in Time and Space The Spreadsheet Approach: Working with numbers (not equations) One relationship, one time period No clear model boundaries …. makes it easy to master! …. but inadequate for modeling complexity!
Local in Time and Space The Spreadsheet Approach: Purchases (Jan) Savings (Jan) 1000 – 95.26 = ?
From cell reference formulas to equations • Translate cell reference formulas to equations: February $1,000 January $95.26 Savings (t) = Savings (t - 1) - Purchases • Reconstruct the structure
Exposé in MS Excel: Tree Diagrams of Causal Drivers make the connections among the VARIABLES visible
Exposé in MS Excel Two distinguished tree diagrams Tree Diagrams of Precedence Tree Diagrams of Causal Drivers
Can we build on what people know? The Value Proposition: Global (interconnected) System Dynamics Complex Issues Spreadsheet Local (isolated) Simple Issues Short term Long term
From Numbers to Equations and back again The Value Proposition: Exposé allows the user to interact with Numbers and Equations any time in the process of modeling Sometimes it might be easier to start with Numbers and then move to Equations
Sometimes, wouldn’t be easier to start with… Example: From Numbers to Equations and back again Purchases (Jan) Savings (Jan) 1000 – 95.26 = ?
….. in order to arrive at…..? Example:From Numbers to Equations and back again Savings = Integ( purchases, 1000)
One way linkages: The Spreadsheet Approach: Lack of focus on integration point and feedback processes makes spreadsheets inadequate to model dynamic systems
Exposé in MS Excel Make integration points visible Launch Exposé with Examples from the book
Exposé in MS Excel Circular Causality Identify and work with feedback processes Launch Exposé with Examples from the book
Exposé in MS Excel Allows data-point non-linearity Launch Exposé with the MARKET GROWTH MODEL
Exposé in MS Excel Do “what if” analysis more often Launch Exposé perhaps with Market growth model