Question

An experiment is conducted in order to determine how different dosages of Vitamin D affect bone mineral density in individuals over the age of 70 years. Researchers are able to recruit 379 volunteers over the age of 70 to participate in the experiment. Each individual is randomly assigned to be given one of three doses of Vitamin D—either 300, 600, or 1200 micrograms—once a month over the course of one year. At the start of the experiment, bone mineral density is measured for each individual. It is then measured again at the end of the study. The researchers observed no statistically significant changes in bone mineral density among the three Vitamin D dosage levels. Based on what you know about experiments in general, in addition to the details of this particular experiment, which one of the following statements is true?

A. If the researchers know who is getting which dosage but the subjects do not know, we would call this a double-blind study.

B. Random assignment is a way to help control for possible lurking variables.

C. There was a placebo used in this experiment.

D. It’s not possible to generalize or extend the results to the population unless the results are found to be “statistically significant.”

Answer 1