Pakistan study notes for Matric, Intermediate, B.A, B.COM BSC, M.A, BCS. Free Pakistani Urdu educational school, colleges and University notes.

ERROR AND DEVIATION

ERROR AND DEVIATION

We know that in experimental observations we come across with errors and deviations in repeated measurements due to the factors like defect in the instrument”, or “Lack in handling the apparatus”, or “improper functioning of the instrument” etc. Errors in analysis may be classified a systematic (determinate) and as random (determinate).

Systematic errors are caused by the defect in the analytical method or by the improper functioning of instrument. For example, in titration s if the indicator is not properly prepared, then the cooler change will occur before the equivalence point, this systematic error or if burette is not properly cleaned or rinsed, then it will cause a systematic error. To avoid this type of error, the cause of error should be rectified. There is no strict definition of systematic errors, since what is a systematic error for one experiment may not be for another.

Nevertheless, when all the systematic errors have either been eliminated or corrected for, we still do not obtain “exact” or ‘true” measurements because there is some uncertainty in every physical measurement. The errors that the remaining variations indicate are called random errors. Random errors are unavoidable for example in a 50cm3 burette, we can read the burette reading accurately only to the nearest 0.1 cm. A random error may be positive or negative. That is why we take the average of the several replicate measurements which is more reliable than any individual measurement.

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