Uncertainties and errors

Uncertainties

Comprehend the nature of uncertainties as the unpredictable, inevitable variations that occur in all measurement.
Recognise that measured values are actually ranges characterised by a best estimate (the measured value) and an uncertainty (the “spread” of this range).
Identify random uncertainties/ errors as those that cause readings to be spread about some central value in a random way. They arise from unpredictable and essentially uncontrollable variations in readings.
Understand systematic uncertainties/errors as those that cause readings to vary in a predictable way from the true value. They result from faults in the measurement system, such as zero error.

Develop an understanding of absolute uncertainty, which is expressed in the same units as the measurement and characterises the “spread” around a best estimate.
Recognise the concept of percentage uncertainty to express the absolute uncertainty as a fraction of your best estimate and thus compare the “sizes” of uncertainties between different measurements.

Get to grips with uncertainty propagation, which is the process of determining the uncertainty of a quantity derived from several other quantities.
Practise propagating uncertainties for quantities calculated through addition or subtraction, for which absolute uncertainties add.
Master propagating uncertainties for quantities calculated through multiplication or division, where percentage uncertainties should be added.

Get the hang of repeating measurements and calculating the mean to reduce random uncertainties.
Learn calibration, zeroing of readings, and using a high precision instrument to minimise systematic errors.
Apply correct experiment design and setup to prevent avoidable errors and uncertainties.

Remember to always express final results including their appropriately derived uncertainties.