Simplify the following text for a Grade 15 native English-speaking person.
Original: In the study of communicable and non-communicable diseases , epidemiologists are involved in outbreak investigation to study design , data collection , statistical analysis , documentation of results and submission for publication .
Simplified: Epidemiologists work from outbreak investigation to study design , data collection and analysis including the development of statistical models to test hypotheses and the documentation of results . Epidemiologists also study the interaction of diseases in a population .