BRAINCAKERandom and Systematic Errors
No measurement is perfect. OCR separates errors into two types.
Random errors cause readings to scatter unpredictably about the true value, some too high and some too low. They come from things such as human reaction time when using a stopwatch, readings that fluctuate, or judging a position by eye differently each time. Random errors cannot be removed, but their effect can be reduced by repeating readings and calculating a mean, or by plotting a graph and drawing a line of best fit.
Systematic errors shift every reading by the same amount (or the same proportion) in the same direction. Repeating the readings does not reduce them, because every repeat has the same error. Causes include a badly calibrated instrument, always reading a scale from the same wrong angle (parallax), or a zero error.
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More in Measurements and Uncertainties
- Precision and Accuracy
- Absolute and Percentage Uncertainty
- Combining Uncertainties
- 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