Experimental error a fact of scientific life.

            Experimental error is always with us; it is in the nature of scientific measurement that uncertainty is associated with every quantitative result. This may be due to inherent limitations in the measuring equipment, or of the measuring techniques, or perhaps the experience and skill of the experimenter. However mistakes do not count as part of the analysis, though it has to be said that some of the accounts given by students dwell too often on mistakes blunders, let's not be coy    and too seldom on the quantitative assessment of error. Perhaps it's easier to do so, but it is not quantitative and does not present much of a test of the quality of the results.

            The development of the skill of error assessment is the purpose of these pages. They are not intended as a course in statistics, so there is nothing concerning the analysis of large amounts of data from, for example, biological populations. Rather they are intended to help you assess error in, say, a titration experiment; or perhaps in results used to determine enthalpies of neutralisation.

            The pages cover the following topics:

  • Combining experimental error. Where two measurements, each of which has an error associated with it, are combined (for example subtracting two volumes to get the titre in volumetric analysis) there will be an error in the result. This is not simply related to the magnitudes of the individual errors; it is unlikely that these will both combine in the same direction, so simple combination gives a pessimistic assessment of overall error.

Origins of error    Combining error    Chemistry contents     Home page