Аннотация
In this article we present the main methodological principles of planning and performing ecological (correlation) studies as well as the principles of statistical analysis of data obtained in ecological studies. The theoretical background of this study design, its main advantages and disadvantages are presented. We also describe research questions that can be studied using ecological study design. Step by step instructions for statistical data analysis using free online calculators are presented. Correlation coefficients and their interpretation are described using example from real studies. Examples of ecological studies from the literature including examples from the Arkhangelsk region are presented.