Difference Between Systematic and Random Error

It becomes almost impossible to avoid errors totally when you are trying to take the exact measurements, or facing problems with the equipment. The measurements of physical quantities cannot always be the correct values.

In order to avoid such errors, scientists try to classify errors and remove uncertainties in the measurements made by them.

There are two main kinds of errors- Systematic error and Random error. Knowing about systematic and random errors helps us to perform the experiments better and to reduce errors.

Systematic vs Random Error

The main difference between systematic and random error is that systematic errors occur because of incorrect or imperfect equipment. Because of the imperfect apparatus, each measurement taken will be incorrect by the same amount. On the other hand, random errors occur because of unavoidable disturbances or due to problems that you face when taking measurements of quantities that change with time.

Systematic vs Random error


Comparison Table Between Systematic and Random Error

Parameters of ComparisonSystematic ErrorRandom Error
MeaningA systematic error is an error that arises because of fault in the measuring device.A random error is an error that arises because of unpredictable changes in the environment.
RepetitiveSystematic errors are repetitive.Random errors are not generally repetitive.
CausesFlaws in the experimenting equipment.Unpredictable variations in readings, disturbances in the environment.
ReductionSystematic errors can be reduced by using the correct apparatus or proper techniques.Random errors can be reduced by taking the readings time and again and increasing the number of observations.
TypesThree types: Instrument, Environment, Systematic error.No types.
ReproducibleThese are reproducible.These are not reproducible.
Magnitude of errorConstantVary


What is Systematic Error?

Systematic error is also known as systematic bias. These errors are consistent errors that can be repeated because of the flawed experimental design.

Sources of systematic errors:

  1. Incorrectly calibrated instrument
  2. Worn out instrument
  3. An individual taking the measurement incorrectly

There are three types of systematic errors:

  1. Instrumental error- Basically, there are three causes of instrumental errors:
    1. Misuse of the experimental setup.
    1. When the mechanical structure of the set up is not perfect.
    1. When there is a loading effect.
  2. Observational error- Observational error arises when the observer does not interpret the readings correctly.
  3. Environmental error- When there are changes in the surroundings such as pressure, humidity, and so on, it may give rise to environmental errors.

What is Random Error?

As the name suggests, a random error is irregular in nature and it is not possible to be forecasted. Such errors arise when there are some limitations that are not in control of the experimenter.

Random error is also known as statistical error. This is so because such errors can be eliminated by statistical means because it is irregular and inconsistent in nature.

Unlike systematic errors, random errors can be decreased by taking the observations repeatedly and taking the average of a large number of observations.

Main Differences Between Systematic and Random Error

  1. Systematic errors are reproducible whereas random errors are not reproducible.
  2. The magnitude of error is constant in systematic errors while it may vary in random errors.



When we measure a physical quantity, we cannot always get the exact true value of it. There are always some errors involved in it. The two most common errors are systematic error and random error.

Basically, systematic errors occur because of the faulty mechanical structure of the measuring instrument whereas the random error occurs because of unpredictable disturbances in the surroundings such as changes in the pressure, temperature.

Eliminating both the errors completely is not possible. However, if tried, all systematic errors can be removed, but there might still remain some random errors in the measurement.


  1. https://journals.ametsoc.org/mwr/article/121/1/173/65053
  2. https://journals.ametsoc.org/jhm/article/17/4/1119/342820
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