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Types of Errors
Random error:
an error in measurement caused by factors that vary from one measurement to another.
- Present in all measurements
- May be due to human errors
- Cannot be predicted, hence cannot be avoided
- Reading can fall above or below the actual value
- Can be mitigated through taking repeated measurements OR reading multiple at once (random error is split among multiple objects)
Example of random error: Parallax error
Due to incorrect positioning of eyes when taking readings
Systematic error:
an error having a non-zero mean, so that its effect is not reduced when observations are averaged.
- Present in all measurements, an accurate reading has a small systematic error
- May be due to human errors or faulty instruments
- Causes a set of results to be displaced evenly from the actual value
- Minimised by method of difference/measuring known value and taking offset
Example of systematic error: Zero error
Due to the imperfect alignment of the zero marks between the main and smaller scales.
- Reading when the value should be 0 = Zero Error
- Accurate Measurement = Final Reading – Zero Error
- Especially in Vernier Calipers and Micrometer Screw Gauge