Final answer:
The number of researchers involved influences how many quadrat plots are used in population studies. Quadrat plots are used to estimate population size and density.
Step-by-step explanation:
The factor that influences how many quadrat plots are used in population studies is the number of researchers involved.
Quadrat plots are used to count the number of individuals within a specific area and estimate population size and density. The more researchers involved, the more quadrat plots can be placed in different locations, providing a more accurate representation of the population.
Availability of funding for the study is not directly related to the number of quadrat plots used, but it can indirectly influence the number of researchers involved in the study, which in turn affects the number of quadrat plots used.