Accurately Precise and Precisely Accurate: An Experimental Comprehension

Shaikh. Mohiuddin^1, and Zahida Karim¹

¹Department of Chemistry, University of Karachi, Karachi, Pakistan

Cite this paper:
Shaikh. Mohiuddin and Zahida Karim. Accurately Precise and Precisely Accurate: An Experimental Comprehension. World Journal of Chemical Education. 2015; 3(2):40-45. doi: 10.12691/wjce-3-2-3

Abstract

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.

Keywords:
accuracy precision second year undergraduate analytical chemistry graduate education/research

This work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

References:

[1]	Paul, S. M., “The Importance and Efficacy of Using Statistics in the High School Chemistry Laboratory,” Journal of Chemical Education, 83(11). 1649-1651. Nov. 2006.
[2]	Walter, R. C. “Practical precision for chemistry students,” Journal of Chemical Education, 29(7). 349-352. Jul.1952.
[3]	Buehrer, T. F. and Schupp, O. E. Jr., “Student precision in quantitative analysis. I. Factors influencing precision” Journal of Chemical Education, 3(12). 1271-1276. Nov.1926.
[4]	Jordan, A. D., “Which Method Is Most Precise; Which Is Most Accurate?,” Journal of Chemical Education, 84(9). 1459-1460. Sep.2007.
[5]	Richard, S. T., “Precision and Accuracy in Measurements: A Tale of Four Graduated Cylinders,” Journal of Chemical Education, 75 (8). 992-995. Aug.1998.
[6]	Piskulic, L., Racca, L., Bottai, H. and Leiva, M., “Accuracy and Precision in Measurements: Two Complementary Approaches,” Teaching Statistics: An International Journal for Teachers, 28(1). 14-16. Feb.2006.
[7]	Hui, L., Chi-Fu, Y. and Sanjeevi, S.. “Fluorescence Axial Localization with Nanometer Accuracy and Precision,” Nano Letters, 12(7). 3731-3735. Jun.2012.
[8]	Matthew, A. W., Andreas, V. and Rohit, V. P., “New Estimators for Calculating Solvation Entropy and Enthalpy and Comparative Assessments of Their Accuracy and Precision,” The Journal of Physical Chemistry. B., 114(24). 8166-8180. May.2010.
[9]	Leonard, I. W., Tyler, B. C., and Pradeep, K. A., “Approaches for Achieving Long-Term Accuracy and Precision of δ18O and δ2H for Waters Analyzed using Laser Absorption Spectrometers,” Environmental Science and Technology, 48(2). 1123-1131. Dec.2014.
[10]	Feng, Y. and Max, L., “Accuracy and Precision of a Custom Camera-Based System for 2-D and 3-D Motion Tracking during Speech and Nonspeech Motor Tasks,” Journal of Speech, Language, and Hearing Research, 57(2). 426-438. Apr.2014.
[11]	Haley, S. M., Coster, W. J., Dumas, H. M., Fragala-Pinkham, M. A., Kramer, J. N., Pengsheng, Tian, F., Kao, Y., Moed, R. and Ludlow, L. H., “Accuracy and Precision of the Pediatric Evaluation of Disability Inventory Computer-Adaptive Tests (PEDI-CAT),” Developmental Medicine & Child Neurology, 53(12). 1100-1106. Dec.2011.
[12]	Hartkopf A. V. “Significance and precision” Journal of Chemical Education, 64 (12), 1068, Dec.1987.
[13]	Marc, T. S., “Accuracy vs. Precision - What is more important for Process Capability” Elsmar Cove Disscussion Forum, 1(6), 6. Jul.2007.
[14]	Miller, J.C. and Miller, J.N., Statistics and chemometrics for analytical chemistry, 6th Edition, Pearson Education, Canada, 2010.
[15]	Belcher, R. “The application of chelate compounds in analytical chemistry,” Pure and Applied Chemistry, 34(1), 13-27, Jan.1973.
[16]	Skoog, D. A., Holler, F. J. and Crouch, S. R., Principles of Instrumental Analysis, 6th Edition, Thomson Brooks/Cole, Belmont, CA, 2007.