In this paper statistical approach is applied to electro-optical investigation of electric properties and sizing of colloidal panicles. Although the main attention is paid to colloid systems, the main principles may be extended to macromolecular solutions. Theoretical description of electro-optical effects in colloidal systems and macromolecular solutions results in Fredholm integral equations of the first kind for the particle distribution in their parameters, such as dipole moment, size, coefficient of rotary diffusion. Regularization technique is applied to solution of these equations and its feasibility is tested. The investigation of particle interaction and the determination of relations between different particle parameters can be carried out taking into consideration the distribution of particles on their parameters. The main principles of the paper are supported by experimental results.