Watch and read the links to find answers to the questions
http://epiphanyvideoworks.com/Science/Hughes/Units/ScientificMethodContent.htm
http://www.biology-pages.info/E/Epidemiology.html
https://www.ck12.org/earth-science/modelling-in-earth-science/lesson/Scientific-Models-HS-ES/
https://www.ck12.org/chemistry/modeling/lesson/Scientific-Modeling-MS-PS/