World Journal of Chemical Education, 2015, Vol. 3, No. 2, 40-45 Available online at http://pubs.sciepub.com/wjce/3/2/3 © Science and Education Publishing DOI:10.12691/wjce-3-2-3 Accurately Precise and Precisely Accurate: An Experimental Comprehension Shaikh. Mohiuddin * , Zahida Karim Department of Chemistry, University of Karachi, Karachi, Pakistan *Corresponding author: shmohiuddin@uok.edu.pk Received March 28, 2015; Revised April 10, 2015; Accepted April 15, 2015 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 Fe 2+ 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 Cite This Article: Shaikh. Mohiuddin, and Zahida Karim, “Accurately Precise and Precisely Accurate: An Experimental Comprehension.” World Journal of Chemical Education, vol. 3, no. 2 (2015): 40-45. doi: 10.12691/wjce-3-2-3. 1. Introduction Statistics is an essential tool for quality analytical chemistry [1]. The prime target of using statistics is to have accurate and precise outcomes of analysis. Stories about accuracy and precision are not new, people are always worried about it [2,3]. This is well-known concept that closeness of data is precision and closeness of results or its mean value to the true or actual value is accuracy. Several attempts have been made in past to nourish the concept of accuracy and precision in the field of chemical education (4). Experiments and pedagogical contents have been reported for good understanding of the concept of basic statistics, especially accuracy and precision [5,6]. Other chemical analysis [7,8] as well as disciplines covering other than science subjects are also emphasis on accuracy-precision differentiation even in topic of articles [9,10,11]. 1.1. Real Time Teaching and Learning This is an approach to discuss the concepts within lab or during experiment. In this experiment, a collective data is used and students are gathered to discuss data and do calculation to appreciate concepts. At each step students are asked reason(s) for any expected and unexpected matter, details are demonstrated in discussion section. This gives chance to students to actively think and practice their concepts. Most of the concepts canvassed in this article are commonly known, but it is always better to practically appreciate them. 1.2. Which Comes First? Accuracy or Precision An important thing that is discussed (prior to experiment) is preference among accuracy and precision. Both are important but which one has priority, it has to be understood. Usually people have different misconceptions in treatment of data [12]. One of those is about giving preference to accuracy or precision. A website has been visited in August 2011 and also cited in this article [13] showing a poll for choosing more important among accuracy and precision. In such poll out of 22 participants, 12 gave preference to accuracy over precision. This is not necessary to have same results of such polls every time but usually the students of chemistry or analytical chemistry also give importance to accuracy over precision. That argument is exercised in current study. Details are specified in subsequent text (see section 4.1.). 1.3. Why Standard Deviation? Since precision is the closeness to the mean value of data, therefore deviation (i.e. difference of each data point with mean) can be one of the tools to know closeness of