Error - sources of errors - classification of error - compare systematic error and random error

 Error - sources of errors - classification of error - compare systematic error and random error

An error may be defined as the difference between the measured and actual values. For example, if the two operators use the same device or instrument for measurement. It is not necessary that both operators get similar results. The difference between the measurements is referred to as an ERROR.


To understand the concept of measurement errors, you should know the two terms that define the error. They are true value and measured value. The true value is impossible to find by experimental means. It may be defined as the average value of an infinite number of measured values. The measured value is a single measure of the object to be as accurate as possible.


Types of Errors

There are three types of errors that are classified based on the source they arise from; They are:

Gross Errors

Random Errors

Systematic Errors

Gross Errors

This category basically takes into account human oversight and other mistakes while reading, recording, and readings. The most common human error in measurement falls under this category of measurement errors. For example, the person taking the reading from the meter of the instrument may read 23 as 28. Gross errors can be avoided by using two suitable measures, and they are written below:

Proper care should be taken in reading, recording the data. Also, the calculation of error should be done accurately.

By increasing the number of experimenters, we can reduce the gross errors. If each experimenter takes different readings at different points, then by taking the average of more readings, we can reduce the gross errors

Random Errors

The random errors are those errors, which occur irregularly and hence are random. These can arise due to random and unpredictable fluctuations in experimental conditions (Example: unpredictable fluctuations in temperature, voltage supply, mechanical vibrations of experimental set-ups, etc, errors by the observer taking readings, etc. For example, when the same person repeats the same observation, he may likely get different readings every time.

This article explored the various types of errors in the measurements we make. These errors are everywhere in every measurement we make. To find more articles, visit BYJU’S. Join us and fall in love with learning.


Systematic Errors:

Systematic errors can be better understood if we divide them into subgroups; They are:

Environmental Errors

Observational Errors

Instrumental Errors

Environmental Errors: This type of error arises in the measurement due to the effect of the external conditions on the measurement. The external condition includes temperature, pressure, and humidity and can also include an external magnetic field. If you measure your temperature under the armpits and during the measurement, if the electricity goes out and the room gets hot, it will affect your body temperature, affecting the reading.


Observational Errors: These are the errors that arise due to an individual’s bias, lack of proper setting of the apparatus, or an individual’s carelessness in taking observations. The measurement errors also include wrong readings due to Parallax errors.


Instrumental Errors: These errors arise due to faulty construction and calibration of the measuring instruments. Such errors arise due to the hysteresis of the equipment or due to friction. Lots of the time, the equipment being used is faulty due to misuse or neglect, which changes the reading of the equipment. The zero error is a very common type of error. This error is common in devices like Vernier callipers and screw gauges. The zero error can be either positive or negative. Sometimes the scale readings are worn off, which can also lead to a bad reading.


Instrumental error takes place due to :

An inherent constraint of devices 

Misuse of Apparatus 

Effect of Loading

Errors Calculation


Different measures of errors include:

Absolute Error

The difference between the measured value of a quantity and its actual value gives the absolute error. It is the variation between the actual values and measured values. It is given by 


Absolute error = |VA-VE|


Percent Error

It is another way of expressing the error in measurement. This calculation allows us to gauge how accurate a measured value is with respect to the true value. Per cent error is given by the formula


Percentage error (%) = (VA-VE) / VE) x 100


Relative Error

The ratio of the absolute error to the accepted measurement gives the relative error. The relative error is given by the formula:


Relative Error = Absolute error / Actual value


How To Reduce Errors In Measurement

Keeping an eye on the procedure and following the below listed points can help to reduce the error.


Make sure the formulas used for measurement are correct.

Cross check the measured value of a quantity for improved accuracy. 

Use the instrument that has the highest precision.

It is suggested to pilot test measuring instruments for better accuracy.

Use multiple measures for the same construct. 

Note the measurements under controlled conditions.

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