When one uncertain number could change the decision, do not hide it inside a single average.
- Low: A cautious result you can reasonably imagine.
- Likely: The figure you currently believe is most plausible.
- High: A better result that is still credible.
This works for income, rent, renovation cost, interest rates or business revenue.
Compare what remains true across all three. If the possibility works even in the low scenario, that gives confidence. If it only works in the high scenario, you have found the assumption that needs testing.