Fractures of the spine are common and serious among women with advanced osteoporosis (low mineral density in the bones). Can taking strontium ranelate help? A large medical trial was conducted to investigate this question. Researchers recruited 1649 women with osteoporosis who had previously had at least one fracture for an experiment. The women were assigned to take either strontium ranelate or a placebo each day. All the women were taking calcium supplements and receiving standard medical care. One response variable was the number of new fractures over 3 years.

a. Describe a completely randomized design for this experiment.

b. Explain why it is important to keep the calcium supplements and medical care the same for all the women in the experiment.

c. The women who took strontium ranelate had statistically significantly fewer new fractures, on average, than the women who took a placebo over a 3-year period. Explain what this means to someone who knows little statistics.