Evaluate the following generalization(s), identifying sample, population, attribute of interest, and the extent to which the claims involved are knowable. Consider carefully the size and diversification of the sample and the extent to which the population differs or may differ from the sample; remember, what's important is that the sample be representative.Osteoporosis is a degeneration of bone tissue that afflicts between fifteen and twenty million Americans and leads to approximately 1.3 million bone fractures every year. The condition is found mainly among women. A conference sponsored by the National Institutes of Health in 1994 reported that calcium was one of the "mainstays of prevention and management of osteoporosis." In a localized study designed to help predict the future

Question

incidence of osteoporosis in women in a midwestern community, a county hospital did a survey on calcium intake. It selected five hundred women at random and asked them to keep a record of their food and dietary supplements for one month. The data were analyzed to determine the amounts of calcium each woman received. It was determined that 85 percent of the surveyed women received less calcium than the recommended amount of 1,000 to 1,500 milligrams per day. County medical authorities concluded that about 85 percent of the community's women were getting less than the recommended intake of calcium. They also concluded that local medical facilities would soon see an increase in the number of cases of osteoporosis as the calcium deficiency showed its effects. Given just the information presented here, how much confidence would you have in these conclusions?

What will be an ideal response?

Answer 1

The first conclusion is less solid than it might appear. The survey was done during one month, and diets change during the course of a year. More dairy products may be consumed during one time of the year than others; certainly some vegetables are consumed on a varying seasonal basis. Hence, the study may accurately reflect only the calcium intake in the population during that month of the year. Another problem with the survey is that the women were categorized by age. Women of different ages may consume different amounts of calcium, and since osteoporosis is a degenerative condition, it is likely to affect women of different ages much differently. (Women who take too little calcium at age twenty-four but who increase their intake by the time they are thirty-five may be no more likely to suffer osteoporosis than those whose intake is high during their entire lives.)
The second conclusion does not follow at all. The insufficient intake of calcium may have been going on for years; so the incidence of osteoporosis may remain exactly the same in the future.