Question

A farmer conducts an experiment to determine whether type of fertilizer (A or B) impacts the concentration of Vitamin C in the blueberries he grows. Of 20, well-spaced blueberry bushes, he randomly assigns 10 to receive fertilizer A. The remaining 10 bushes receive fertilizer B. At harvest time, he collects 5 blueberries at random from each bush and measures their Vitamin C concentration (so that he ends up with 20×5=100 measurements altogether).

a. What are the factor(s) in this experiment and what are their corresponding levels?

b. What are the individuals in this experiment? (1 mark)

c. Did the farmer use a completely randomized design? Explain.

d. After doing a (correct) statistical analysis, the farmer finds that the blueberries that received fertilizer A had significantly higher concentrations of Vitamin C than those that received fertilizer B, on average. Would you suspect that the difference in fertilizers caused this difference, or that a confounding factor was at play? Explain and, if the latter, provide a plausible example of such a factor.

Answer 1