__________ determines whether subject-based or population-based RI is more informative

• A. Analytical variation
• B. Inter-individual variability
• C. Index of Individuality (II)
• D. Within-population variance

Answer: (C)

The key idea is how much variation we see within the same person over time compared to variation between different people. This ratio guides whether a population reference interval or a subject-specific interval will be more informative. The index of individuality is that ratio: it compares within-subject variation to between-subject variation. If the index is small, most people cluster around the same population range and a population-based reference interval works well. If the index is large, an individual’s own baseline fluctuates more than the differences seen between people, so using a subject-based reference interval provides more meaningful interpretation. Thus, the index of individuality determines which type of reference interval is more informative.