alleryStart learning →A doctor reports that a patient's blood pressure has a z-score of 1.75. Which reading is correct?
AIt sits 1.75 points above the average
BIt is 1.75 times the usual reading
CIt sits 1.75 standard deviations above
DIt is exactly 175 units of pressure
Answer & Solution
Correct answer: C. It sits 1.75 standard deviations above
1. A z-score is measured in standard deviations, not in the original units.
2. The sign is positive, so the reading lies above the average.
3. The size is 1.75, so it lies 1.75 standard deviations above that average.
4. Reading it as 1.75 points, or as a multiplier, or as 175 units all ignore the standard deviation.
_Source: OpenStax High School Statistics (CC BY 4.0), section 6.1 The Standard Normal Distribution_
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