Ecological Systems and Devices Annotation << Back INFLUENCE OF THE CONFOUNDING ON THE ASSESSMENT OF RADIATION EXPOSURE EFFECT (A CASE STUDY OF ANIMALS OF THE EAST URAL RADIOACTIVE TRACE) L.N. Rasina A.N. Varaksin The determination of the radiation exposure effects on the indices of mammals living in the radioactively contaminated natural areas is considered. To solve the problem animals were harvested and analyzed in laboratory. The situation is considered when the number of animals caught in one year is insuffi cient for the reliable determination of the radiation exposure effect. The analysis of some statistical approaches to assess the impact of year trapping on radioactive exposure is provided. The following approaches are discussed: weighted mean, ANCOVA with factors «Year trapping» and «Ordered year trapping» taken as covariates; and standardization by stratifi cation. It is demonstrated that the most valid method is standardization by stratifi cation. The magnitude of radiation exposure is calculated for 13 indices of fi eld mice collected over the area of East Ural Radioactive Trace (VURS) and in the control areas during 2003 to 2008 period. Difference between estimates calculated by weighted mean and standardization is more than 40 % for particular indices. Recommendations for the procedure of animals trapping in order to assess radiation exposure effect are provided. The most important recommendation is to catch about the same number of animals every year in the experimental (radioactively contaminated) and control (clean) areas. Keywords: radiation exposure; trapping year; statistical analysis; weighted mean; standardization by stratifi cation. Contacts: E-mail: rasina@ipae.uran.ru, E-mail: varaksin@ecko.uran.ru Pp. 28-33.