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Definition of error:Measurement is the foundation of all, experimental science and technology. The result, of every measurement by any measuring, instrument contains some uncertainty. This, uncertainty is called error. Every calculated, quantity which is based on measured values,, also has an error. We shall distinguish between, two terms: accuracy and precision., , Classification of error:The errors in measurement can be, broadly classified as (a) systematic errors and, (b) random errors., Systematic errors:The systematic errors are those errors that, tend to be in one direction, either positive or, negative., Some of the sources of systematic, errors are :, Instrumental errors that arise from the, errors due to imperfect design or calibration, of the measuring instrument, zero error in, the instrument, etc., Imperfection in experimental technique, or procedure To determine the temperature, of a human body, a thermometer placed, under the armpit will always give a, temperature lower than the actual value of, the body temperature., Personal errors that arise due to an, individual’s bias, lack of proper setting of, the apparatus or individual’s carelessness, in taking observations without observing, proper precautions, etc.

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Systematic errors can be minimised by, improving experimental techniques, selecting, better instruments and removing personal bias, as far as possible. For a given set-up, these, errors may be estimated to a certain extent and, the necessary corrections may be applied to the, readings., , Random errors, The random errors are those errors, which occur, irregularly and hence are random with respect, to sign and size. 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), , There are some other error which we can list out:Least count error, The smallest value that can be measured by the, measuring instrument is called its least count., All the readings or measured values are good only, up to this value., The least count error is the error, associated with the resolution of the instrument., For example, a vernier callipers has the least, count as 0.01cm; a spherometer may have a, least count of 0.001 cm. Least count error, belongs to the category of random errors but, within a limited size; it occurs with both, systematic and random errors.