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

Measurement

Measurement is the foundation for all experimental science. All the great technological development could not have been possible without ever increase 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 has along with it a level of uncertainty which is known as an error. This error may arise out of either error in methods or due to a blunder by the experimenter so a 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 a measurement, it is not necessary that they may get the 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. Measured value is a single measuring of the object with the aim of being as accurate as possible.

There are three types of errors that are classified on the basis of the source they arise from;

Gross Errors: This category basically takes into account human oversight and other mistakes while reading, recording and the readings. The most common of 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:

  • A proper care should be taken in reading, recording the data. Also, 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 average of more readings we can reduce the gross errors

 

  • Systematic Errors: Systematic errors can be better understood if we divide it into subgroups;

 

  • 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 aero 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.

Environmental Errors: This type of error arises in the measurement due the effect of the external conditions on the measurement. The external condition includes temperature, pressure, and humidity and can also include 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 individual’s  carelessness in taking observations. The measurement errors also include wrong readings due to Parallax errors.

Random Error: 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 (e.g. 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 measurements we make. These errors are everywhere in every measurement we make. To find more articles, visit BYJUs.com. Join us and fall in love with learning.


Practise This Question

A point mass m is suspended from a light thread of length l, fixed at O, is whirled in a horizontal circle at constant speed as shown.  From your point of view, stationary with respect to the mass, the forces on the mass are