Market mechanism characteristic for a market economy requires economic entities to apply the rules of economic calculus. Economic analyses are a prerequisite of an adequate functioning of enterprises in the environment of free-market competition. Certain elements of the calculus may also be applied to the analysis of the stock exchange capital investment. There are the following basic features of capital investment: rate of return on the capital invested and risk. The former one is understood as a relation between profit/loss on the investment and capital invested. The article presents theoretical knowledge on the rate of return and empirical calculations based on the Warsaw Stock Exchange Index. The latter part of the article presents also a method of calculating the probability of achieving projected rate of return.

Risk is an inherent part of each economic venture. It is also present in the stock exchange investment. The article presents classical approach to identifying risk of a security, i.e. calculation of standard deviation. From the point of view of an investor, however, it seems more effective to calculate risk based on standard semi-deviation. The method takes into account negative, undesirable deviations of the rate of return from its expected value.