Home | Excel | Power BI | Copilot | Visualising Data
Specify Phase | Spreadsheet Modelling Best Practices (SMBP) Course
The specify phase considers how the model logically produces the required outputs. The benefits include:
- ensures model solves the right problem,
- forces sponsors and model builders to think through the problem and approach,
- surfaces ambiguity, constraints and trade-offs early,
- establishes a common understanding among the stakeholders, and
- makes subsequent phases easier and more effective
The problems that may arise if we don’t do the specify phase include:
- building the model takes longer than anticipated,
- frequent changes introduce more errors,
- the design may be haphazard, and
- the model is deemed a failure and gets thrown away.
How to specify
- Define the outputs (reports, which you should partly have from the scope).
- Determine the calculations and relationships.
- Determine the inputs (assumptions).
Define the outputs
- What reports are needed?
- Who will use them?
- What purpose does each report serve?
- What information should each report show?
- What time periods should be used?
Determine the calculations and relationships
Two possible methods are bubble diagrams (which we will demo) and prototype models. Here is an example bubble diagram
Prototype models
- are useful if the problem is not well defined
- communicate progress easily
- sponsors can provide feedback more easily.
- clarifies what is and is not possible.
- Identify the inputs from the bubble diagrams.
- Check the availability of the data. Is it the “right” data? Any constraints on the data?
- Consider how data can be validated.
- Identify constants e.g., VAT rate.
Coffee Cart - Specify Exercise
Follow the instructions for the Specify phase of the coffee cart case study.