(a) A person's blood pressure is measured to be 120 ± 2 mm Hg120 ± 2 mm Hg . What is its percent uncertainty? (b) Assuming the same percent uncertainty, what is the uncertainty in a blood pressure measurement of 80 mm Hg?
Question
(a) A person's blood pressure is measured to be 120 ± 2 mm Hg120 ± 2 mm Hg . What is its percent uncertainty? (b) Assuming the same percent uncertainty, what is the uncertainty in a blood pressure measurement of 80 mm Hg?
Solution
(a) The percent uncertainty can be calculated using the formula:
Percent Uncertainty = (Absolute Uncertainty / Measurement) * 100%
Here, the absolute uncertainty is ±2 mm Hg and the measurement is 120 mm Hg.
So, Percent Uncertainty = (2 / 120) * 100% = 1.67%
(b) If the same percent uncertainty is assumed for a blood pressure measurement of 80 mm Hg, the absolute uncertainty can be calculated using the formula:
Absolute Uncertainty = (Percent Uncertainty * Measurement) / 100%
So, Absolute Uncertainty = (1.67 * 80) / 100 = ±1.34 mm Hg
Therefore, the uncertainty in a blood pressure measurement of 80 mm Hg is ±1.34 mm Hg.
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