The return for a portfolio consisting of n securities will be based on the return for each of the securities as well as the proportion of the portfolio invested in each security: 1 n i i i r p x    where r is the return of the portfolio, pi is the proportion of the portfolio invested in security i, and xi is the return of security i. typically, we wish to maximize the return, r, but that is subject to constraints regarding the risk that we can tolerate. for a given risk level, we wish to set our proportions, pi, to maximize the return. the variance of the return of the portfolio is a measure of the risk. the variance of the return is calculated as

There are some other ways to act scenario analysis. The standard method is to decide the standard deviation of regular or monthly safety returns and so calculate what amount is required for this portfolio if each security yields returns that exist two or three standard deviations above and below the average performance. This means the analyst may get a fair amount of certainty considering the difference in the value of the portfolio within a given period, by simulating these extremes. Scenarios being thought may refer to one single variable, e.g., the relative success or failure of the current product launching, or the combination of elements, e.g., those results of the product launch combined with possible changes in the activities of competitor businesses. The purpose is to examine the effects of the more extreme results to define an investment strategy.