Final answer:
The term "daily dose of citrus fruit" in Dr. Farrell's study is an operational definition, which specifies how this variable is measured in the research. This is essential for testing hypotheses and ensures the experiment can be replicated by others. Option c is correct.
Step-by-step explanation:
In Dr. Farrell's study, the term "daily dose of citrus fruit" refers to an operational definition. This is the specific way in which the variable of citrus fruit consumption is measured or manipulated in the context of the experiment. In relation to Lind's experiment, the independent variable is the daily supplement received by the pairs, which in this case is the citrus fruit, and it is being used to test its effect on neurogenesis.
The dependent variable would be the observed outcome, that is, the improvement or lack thereof in neurogenesis as a result of the daily citrus fruit dose. Understanding operational definitions is key in experimental design because it allows researchers to precisely test their hypotheses.
Operational definitions are essential for replicating experiments and for other researchers to understand exactly what was measured. The manipulation of variables, such as a daily dose of citrus fruit, and observation of the outcomes, such as the rate of neurogenesis, are central concepts in experimental science. They allow for the establishment of cause-effect relationships and provide a basis for scientific inquiry.