Measurement errors can be categorized in to two
A difference from the true value that is usually constant or proportional to the true value.
How Systematic error can be eliminated?
Identify the source and eliminate if possible or determine size of error and compensate for it in calculations.
What are the sources of systematic error?
Poorly calibrated instrument
Changes in the environment which affect the instrument (e.g high temperature or humidity)
Consistent parallax error in reading a meniscus.
Inherently unpredictable fluctuations in the reading of an instrument or in the experimenters technique.
How this error can be eliminated?
minimize by taking repeated measurement and averaging values.
What are the sources of random error?
Random fluctuations in instrument.