3.35 Calcium and vitamin D. Vitamin D is needed for the body to use calcium. An experiment is designed to study the effects of calcium and vitamin D supplements on the bones of first-year college students. The outcome measure is the total body bone mineral content (TBBMC), a measure of bone health. Three doses of calcium will be used: 0, 250, and 500 milligrams per day (mg/day). The doses of vitamin D will be 0, 75, and 150 international units (IU) per day. The calcium and vitamin D will be given in a single tablet. All tablets, including those with no calcium and no vitamin D, will look identical. Subjects for the study will be 45 men and 45 women.
(a) What are the factors and the treatments for this experiment?
(b) Draw a picture explaining how you would randomize the 90 college students to the treatments.
(c) Use a spreadsheet to carry out the randomization.
(d) Is there a placebo in this experiment? Explain your answer.