Conclusion: The quality and precision of variables used in a plan will decide the fate of any plan. Variables come in many forms: sales, market trends, technological enhancements and so on.
Practical issues, such as the size of any given budget in a plan, may also influence and qualify the variables. Limitations on available resources may influence decisions to account for all relevant variables.
For example, the existing status of technology, or if a competitor has succeeded to your cost, could yield more realistic and sharper variables for planning.
All variables must be included in a general or master, plan, or in the appendix to it. The reason is straightforward, as it will indicate the thought process used to develop the plan and why. This level of information will also assist in subsequent iterations because the elements are discernible.
Two straightforward techniques can improve planning:
By doing so the thought processes within the plan should be focused to everyone involved in the process.