It assists in choosing of variables to be included and those that can logically be omitted from the study. It defines research questions, and focuses on one or more of several aspects of a theoretical model. Systems theory can be applied across disciplines so that universal laws are identified and can be used with individuals, groups, and communities. Developmental Models look at how changes occur based on theories of development of the human organism. Interaction Models are based on philosophical assumptions.
Interaction theory calls attention to how elements affect each other.
The interaction model can be useful in analyzing family dynamics. The Roy Adaptation Model has some of the characteristics of systems theory and some of the characteristics of interaction theory. Her work is studied and utilized frequently in nursing education. Roy's Adaptation Model of nursing relies heavily on the stress theory, the concept of adaptation, and the ability of the nurse to facilitate adaptation to stress. The term adaptation appears frequently throughout the model and is used to describe that which promotes the integrity of the person in terms of survival, growth, reproduction and mastery.