Researchers wish to know if there is a link between hypertension (high blood pressure) and consumption of salt. Past studies have indicated that the consumption of fruits and vegetables offsets the negative impact of salt consumption. It is also known that there is quite a bit of person-to-person variability as far as the ability of the body to process and eliminate salt. However, no method exists for identifying individuals who have a higher ability to process salt. The U.S. Department of Agriculture recommends that daily intake of salt should not exceed 2400 milligrams (mg).
The researchers want to keep the design simple, so they choose to conduct their study using a completely randomized design.
(a) What is the response variable in the study?
(b) Name three factors that have been identified.
(c) For each factor identified, determine whether the variable can be controlled or cannot be controlled. If a factor cannot be controlled, what should be done to reduce variability in the response variable?
(d) How many treatment levels would you recommend? Why?