Systematic Error & Random Error

Systematic Errors

Systematic errors are errors of measurements in which the measured quantities are displaced from the true value by fixed magnitude and in the same direction.

Example of systematic error

  • Zero error
  • Parallax error – viewing consistently from the wrong angle for all readings
  • Environmental conditions – Background radiation in the measurement of radioactive decay.

Systematic errors cannot be eliminated by averaging or by statistical means.

Systematic errors can be avoided by

  • Checking for zero error before taking readings
  • Plotting a graph. If the graph does not cut the expected intercept, the shift is probably due to systematic error.

Random Errors

Random errors are errors of measurements in which the measured quantities differ from the mean value with different magnitudes and directions.

  • Always a good practice to take repeated measurements across different regions of wire when determining the diameter of a thin piece of wire as it may not be uniform

Sources of Random errors

  • Arise from parallax error when an observer reads a scale from an inconsistent direction
  • Variation in environmental conditions
  • Irregularity of the quantity being measured as certain quantities by nature do not follow a regular pattern
  • Limitation of the equipment as certain equipment may be so sensitive that it can detect even the slightest variation on the signals( not a good thing if a general reading is what you want)

Ways to reduce random errors

  • Taking repeated measurements to obtain an average value
  • Plotting a graph to establish a pattern and obtaining the line or curve of best fit. In this way, the discrepancies or errors are reduced
  • Maintaining good experimental technique (e.g. reading from a correct position)

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