Your business plan is only as good as the assumptions behind it. “Assumptions” is a vague word in itself. You can assume based on your “gut”, or you can assume based on the best information you can get.
Startup Venture Toolbox offers a useful Business Proof of Concept Test that, if answered honestly and thoroughly will put your assumptions in the well-educated category. The result will be a good SWOT analysis – of your business Strengths and Weaknesses and the external Opportunities and Threats. The site also offers links to some Toolbox resources that can help you make better assumptions.
Thanks to Anthony Cerminaro for direction to this site.