Accurately Precise and Precisely Accurate: An Experimental Comprehension

摘要

Accuracy and precision are the primary targets in chemical analysis. This article is an experimental approach to appreciate the concepts of precision and accuracy in analytical chemistry. An easy, fast and well-established spectrophotometry experiment for quantitative analysis of Fe2+ is done using 1,10-phenanthroline as a complexing or coloring agent. Real time learning approach is carried out; it means discussing the data in front of class after collection of experimental results. A little data is used to discuss variety of concepts of basic statistics in analytical chemistry. A debate regarding priority of precision over accuracy is done. The objective of using standard deviation (STDEV) and changes in its value by unit conversion or other transformation is explained. The advantage of using relative standard deviation (RSD) is also demonstrated. Several spectrophotometers are compared regarding precision. By using same data, precision of analog and digital spectrophotometers is also compared. Repeatability and reproducibility are also explained and calculated using the same data. Presence of systematic error or accuracy of experiment is statistically assessed without doing further experimentation. The whole study is optionally supported with online MS-Excel worksheets that are automated for better understanding.