Which statement describes the recommended minimum population size from the local community when establishing a reference range?

• A. 10 patients
• B. 25 patients
• C. Large population (minimum 100 patients) from local community
• D. 1000 patients

Answer: (C)

When establishing a reference range, you want a healthy, locally representative sample so the interval truly reflects variation in the population you’ll be testing. The precision of the reference limits depends on how many individuals you include; too small a sample makes the lower and upper bounds unstable and the interval less reliable. Sampling a substantial number of healthy people from the local community captures local demographic and physiological variation, reducing bias from using hospital patients or non-representative groups. A practical minimum that provides reasonable stability is around one hundred individuals. Larger numbers improve accuracy further, but at least about 100 from the local community is a solid, commonly used rule of thumb.