Sensitivity analysis (also called what-if analysis) is a technique which is used to calculate the output variable (e.g. profit, revenues or costs, NPV) under different assumptions (often different sales quantity, selling price, unit variable costs, etc.). It is used during budgeting process and in decision-making, mainly as a method of reducing uncertainty.
A kind of sensitivity analysis is preparation of flexible budgets.
Sensitivity analysis is a technique that can be used during scenario analysis.