Secondly, one people are inclined to over-estimate probability of offensive of unfavorable events and underestimate probability of offensive of positive events, other vice versa, I.e. on of on the same probability psychology names it the effect of context).

However, in spite of these and other nuances, it is considered that probability possesses those mathematical properties, what objective.

A scope of variation is a difference between the maximal and minimum value of factor.

This index gives a very rough estimation a risk, as he is an absolute index and depends only on the extreme values of row.

Dispersion a sum of squares of deviations of casual size from its mean value, self-weighted on the proper probabilities.

Where – the mean or expected value (expected value) of discrete casual quantity is determined as a sum of works of its values on their probability:

The expected value is major description of casual size, as serves as the center of its probability distribution. Sense of it consists in that it shows the most credible value of factor.

Use of dispersion as risk measures not always comfortably, as a dimension of it is equal to the square of metage of casual size.

The results of analysis are more evident in practice, if the index of variation of casual size is shown in those metages, what casual size. For these aims use standard (middle quadratic) deviation.

All above-stated indexes possess one general failing are absolute indexes the values of which predetermine the absolute values of initial factor. Much more comfortable therefore to use the coefficient of variation.

Determination is especially evidently for cases, when the averages of random event differentiate substantially.

In regard to the estimation of risk of financial assets it is necessary to do three remark:

At first, at the comparative analysis of financial assets as a base index it is necessary to take profitability, as a value of profit can substantially vary in an absolute form.

Secondly, the basic indexes of risk at the market of capitals are dispersion and mean quadratic deviation. As as a base a profitableness (profitability) undertakes for the calculation of these indexes, a criterion is relative and comparable for the different types of assets, there is not a sharp need in the calculation of coefficient of variation.

Thirdly, sometimes in literature the above-mentioned formulas are given without the account of weighing on probability. In such kind they are suitable only for a retrospective analysis.

In addition, the criteria described higher it was assumed to apply to normal probability distribution. It, indeed, widely used for the analysis of risks of financial operations, as his major properties (distributing symmetry in relation to middle, insignificant probability of large rejections of casual size from the center of its distributing, rule of three sigma-mesons) an analysis allows substantially to simplify. However much not all financial operations suppose normal distribution of profits (the questions of choice of distributing are considered in more detail hardly below) For example, probability of receipt of profits distributions from operations with derivative financial instruments (and futures) often characterized asymmetry (by a slant) in relation to the expected value of casual size.