BRAINCAKECombining Uncertainties
Results are usually calculated from more than one measurement, so their uncertainties must be combined. The OCR rules are:
• p = x + y or p = x − y: add the absolute uncertainties of x and y. (For p = 2x, the absolute uncertainty in x is doubled.)
• p = xy or p = x/y: add the percentage uncertainties of x and y.
• p = xn: multiply the percentage uncertainty of x by n.
Uncertainties never cancel: even when subtracting, the absolute uncertainties add.
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Key terms in this lesson
- absolute uncertainty
- The uncertainty in a measurement, expressed with the same units as the measurement itself.
- percentage uncertainty
- The absolute uncertainty in a measurement expressed as a percentage of the measured value.
More in Measurements and Uncertainties
- Random and Systematic Errors
- Precision and Accuracy
- Absolute and Percentage Uncertainty
- Uncertainties from Repeated Readings
- Plotting Graphs
- Error Bars
- Best-fit and Worst-fit Lines
- Uncertainty in a Gradient and Intercept
All 12 lessons in Measurements and Uncertainties · All OCR AS-level Physics topics