10. Scenario planning assesses the effect on the success or otherwise of an option of combining different assumptions about the future. A small number of scenarios (typically the optimistic, most likely and pessimistic) is selected and the expected net present cost of each investment option is calculated for each of the chosen scenarios.
11. Each scenario can be tested for sensitivity to changes in key variables. Some key questions to explore under each scenario are:
• does the ranking of the options change under optimistic and pessimistic assumptions?
• how likely are the best and worse case scenarios to arise?
• what would be the effect on affordability and prices to the NHS body of each scenario?
• what would be the effect on value for money of each scenario?