A women's health researcher who studies the relationship between household stress and physiologic markers wants to understand the feasibility of collecting the biomarkers (e.g. cortisol, C-reactive protein) through saliva rather than serum or plasma, as this would facilitate research by allowing for community-based collection of samples. She wants to know the how similar levels of the markers are collected both ways.

What are the variable(s) involved? What type of variables are they (continuous, categorical, etc.)? What statistical analysis test is most appropriate? What are the assumptions of that test? What are the values that test produces that must be interpreted? What research question does your analysis answer?