One of the most important parts of the economic evaluation of industrial processes is sensitivity analysis. It assesses the effect on the process economics of various engineering and economic parameters. A widely used method of sensitivity analysis starts with defining a base or reference case and determining its economics in terms of a criterion, such as cost or profitability. Subsequently, one parameter at a time is varied over a range of values, and the corresponding changes in the selected criterion are estimated. In some cases, the investigator varies two related parameters at the same time. Assume, for example, that it is desired to investigate the effect on profitability of plant capacity, with all other independent variables unchanged. A higher capacity implies the increase in two parameters, capital cost and production, as opposed to the increase in production at constant capital, which can be denoted as attaining higher plant productivity. Capital and production are two distinct parameters. The former, an economic variable, affects cash flow primarily during the construction period; while production, an engineering variable, may have a major impact only after start-up. Rarely are more than two selected parameters varied at the same time in sensitivity analysis. The purpose of this analytical tool would be defeated, as the individual effects would become blurred. The variation of a