Errors in Measurement: Gross Errors, Systematic Errors and Random Errors

Measurements are an integral part of living, we measure time, we measure steps walked to know the calories burnt, we measure the materials added for cooking, and we also measure the size of clothes to know whether it fits perfectly. Sometimes we fail to know the exact measurement and the values vary giving rise to errors. In this article, let us learn about measurement, errors in measurement, types of errors and how to avoid the errors.

Table of Contents:

Measurement

Measurement is the foundation for all experimental science. All the great technological development could not have been possible without ever-increasing levels of accuracy of measurements. The measurement of an amount is based on some international standards which are completely accurate compared with others. Just like your vegetable vendors, measurements are taken by comparing an unknown amount of weight with a known weight. Every measurement carries a level of uncertainty which is known as an error. This error may arise in the process or due to a mistake in the experiment. So 100% accurate measurement is not possible with any method.

An error may be defined as the difference between the measured value and the actual value. 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 that occurs between both the measurements is referred to as an ERROR.

Sequentially, to understand the concept of errors in measurement, 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 measuring of the object with the aim of being as accurate as possible.

Types of Errors

There are three types of errors that are classified on the basis of 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 errors, the human error in the measurement fall under this category of errors in measurement. For example, the person taking the reading from the meter of the instrument he 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 reading 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, it is very likely that he may 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 it 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 thereby 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 calipers and screw gauge. The zero error can be either positive or negative. Sometimes the readings of the scale are worn off and this 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 true value. Percent 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. 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 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.

Frequently Asked Questions – FAQs

What is meant by measurement error?

The difference between a measured quantity and its true value gives measurement error.

What are the types of errors?

The following are the types of errors:

  • Gross Errors
  • Random Errors
  • Systematic Errors

The error seen due to the effect of the external conditions on the measurement is known as?

It is known as the environmental error.

Define absolute error?

Absolute error is the variation between the actual values and measured values. It is given by
Absolute error = |VA-VE|

A length was calculated to be 10.1 feet, but the absolute length was 10.5 feet. Calculate the absolute error.

We know that, Absolute error = |VA-VE|
Absolute error = 10.5-10.1 = 0.4 feet

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