Systematic errors are errors that are consistently in the same direction, they are one-sided errors. A systematic error is a type of error that shows a bias or a trend. It makes your readings too high every time, or too low every time. Systematic errors are often due to a problem that persists throughout the entire mwasurement. The common sources of systematic errors are:

• faulty calibration of measuring instruments,
• poorly maintained instruments, or
• faulty reading of instruments by the user.

Examples of systematic error:
(i) Zero error
(ii) Parallax error: when seen only in one direction.
Systematic errors can be reduced by: recalibrate the instrument, improve instrument resolution, apply correction for identified error, improve procedures, shift to other methods, and change the operators. Note that, the accuracy of measurements subject
to systematic errors cannot be improved by repeating those measurements.