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    A Better Analogy for Reference Ranges

    Reference ranges are like a wide “acceptable temperature” range—being “in range” doesn’t guarantee you’re okay.

    • Labs build reference ranges from the middle 95% of a population
    • Healthy people can test “abnormal” just by math
    • Sick people can fall “normal” if the range is wide
    • Your body may function best in a narrower window

    PRISM is for learning, not diagnosing. It explains what tests measure and how clinicians reason — it never tells you what to conclude, and it doesn't replace your doctor.