Probabilistic methods of risk analysis are based on knowledge of quantity characteristics of the risks accompanying implementation of similar projects and accounting of specifics of the industry, a political and economic situation.
Within probabilistic methods it is possible to analyse and evaluate separate types of risks.
The risk connected with the project is characterized by three factors:
 the event connected with risk;
 risks probability;
 the amount put risk.
Quantitatively to estimate risks, it is necessary to know all possible consequences of the made decision and probability of consequences of this decision.
Allocate two methods of determination of probability:
1. The objective method of determination of probability is based on calculation of frequency to which there are some events.
Frequency at the same time pays off a pas to a basis of actual data.
So, for example, the frequency of emergence of some loss rate And in sales process of the investment project can be calculated by a formula:
f(A)=n(A)/n
where f is the frequency of emergence of some loss rate;
n(A) is number of cases of approach of this loss rate;
n  the total number of cases in statistical selection including as successfully performed, and unfortunate investment projects.
At probabilistic risks assessments in case of lack of sufficient volume of information for calculation of frequencies indicators of subjective probability, i.e. expert evaluations are used.
2. Subjective probability is the assumption of a certain result, based on judgment or personal experience evaluating, but not at a frequency with which the similar result was received in similar conditions.
The important concepts which are applied in probabilistic risk analysis are concepts of an alternative, a condition of the environment, an outcome.
The alternative is the sequence of the actions directed to the solution of some problem.
Examples of alternatives: to purchase or not to purchase the new equipment, the decision on what of two machines differing on characteristics should be purchased; whether it is necessary to introduce in production a new product, etc.
A condition of the environment  a situation on which the person making the decision (in our case  the investor), cannot have an impact (for example, the favorable or adverse market, climatic conditions, etc.).
Outcomes (possible events) arise in case the alternative is implemented in a certain condition of the environment.
It is the certain quantitative assessment showing consequences of a certain alternative at a certain condition of the environment (for example, the profit size, harvest size, etc.).
