Difference Between Systematic and Random Error

You might be very careful while conducting experiments, however, they are still likely to have some experimental errors. 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. It is essential to review the origin of error and how these errors could affect the results when obtaining the results.

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 Error 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. Usually, such errors are produced by using incorrectly calibrated measuring instruments or using the instruments incorrectly.

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. For instance, if the pointer of the voltmeter is set on the scale and the line of vision is not exactly above the pointer, an observational error may arise.
  3. Environmental error- When there are changes in the surroundings such as pressure, humidity, and so on, it may give rise to environmental errors. Such errors can be eliminated by making arrangements to control humidity or temperature.

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. These parameters may disturb the results of the experiment.

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. There are two types of errors: Systematic error and random error. As the name suggests, systematic error is a repetitive error that shows the wrong value of a measurement by the same amount every time. This error is due to the incorrect measuring device. On the other hand, a random error is a type of error that does not repeat and is not fixed in the same direction except incidentally. Such errors are sometimes referred to as statistic errors.
  2. The cause of systematic errors may be some defects in the experimenting apparatus. These errors may arise if the individuals use the setup incorrectly or the setup itself may be incorrect. On the other hand, random errors may arise because of disturbances in the environment or because of unpredictable variations in the readings when the observer is not able to interpret the readings correctly.
  3. Systematic errors occur in one direction only, whereas random errors may occur in any direction.
  4. There are three types of systematic errors- Instrument, Environment, Systematic. There are no types of random errors.
  5. Since systematic errors arise due to fault in the apparatus or fault in human interpretations, they can be removed by changing the incorrect apparatus and using the right measuring equipment and proper techniques. They might be difficult to remove completely. If one takes the measurements repeatedly with the same instrument it will neither remove the error nor reveal it. On the other hand, random errors can be eliminated by taking the measurements repeatedly and increasing the number of observations.
  6. Systematic errors are reproducible whereas random errors are not reproducible.
  7. 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. Random error may also arise if the observer is unable to take the correct readings.

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. Random errors are not as dangerous as Systematic errors.


  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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