S0019 [Source: Lynn et al. (2005). Osteoporos 16:1663-1668.]
Reference ranges are those intervals within which 95% of the values fall for a specific population. In other words, a person whose value falls in a reference range is considered as normal. A study examined a total 4274 subjects (2415 females and 1859 males) from Hong Kong and measured their bone mineral density (BMD). A summary of BMD for females from ages 10 to 80 is provided in the table below.
Q1. Is a BMD of 0.8 for a female of age 20 normal? Explain and state what assumptions, if any, are made.
Q2. Interpret the reported 95% confidence interval for an age of 10.
Q3. From the table, the mean lumbar spinal BMD for females of age 30 was 0.99. Someone asked about the precision of this estimate since it was not obtained from all Hong Kong females of age 30. How would you quantify the precision?
Q4. What could be done if one wanted to increase the precision in Q3?