Use of Control Charts and Scientific Critical Thinking in Experimental Laboratory Courses: How They Help Students to Detect and Solve Systematic Errors

Juan M Sanchez

doi:10.1021/acs.jchemed.0c00885

Abstract

Systematic errors are unfortunately common in analyses performed by students in teaching laboratories. Quality control (QC) tools are required to detect and solve bias in laboratory analyses. However, although QC has become routine in real-world laboratories, it is still rarely applied in teaching laboratories. For this reason, systematic errors in students’ results remain unknown in many cases. In this study, the use of control charts and critical thinking methodologies are applied in laboratory lessons to show students how the control charts can be used to detect and correct systematic biases in analyses. Students practice how to evaluate out-of-control results by applying scientific critical thinking procedures based on knowledge acquired in previous subjects, aiming to find the source of the bias detected, solve it, and apply rectifying measures to improve the operational procedure. With the proposed methodology, students understand the importance of control charts in demonstrating the quality and validity of the data obtained. During the academic years applying this methodology, the most common source of bias was found to be related to an incorrect application of basic laboratory skills, which shows that these skills need to be learned and, most importantly, put into practice over the whole period of student training and cannot be taken for granted once they have been taught in the early stages of their curricula. The learning outcomes were assessed through an exercise that requires students to evaluate results obtained in the laboratory in previous years. It was found that the majority of students (97.6%) were able to detect a bias, find the source, and solve the error.

Highlights

Systematic errors are common in analyses performed by students in teaching laboratories
It was observed that some students had problems with some basic laboratory skills, with the calculations to prepare the calibration standards and the selection of the laboratory material required for the correct preparation of a solution since this information was not fully detailed in the procedure
The results obtained in the present study have shown that the use of control charts in laboratory lessons is a useful tool for students to analyze the quality and validity of their experimental results

Summary

Introduction

Systematic errors are common in analyses performed by students in teaching laboratories. Real-world analytical laboratories deal with problems that go well beyond the realm of analyses performed in teaching laboratories,[1] and social, legal, and economical decisions often have to be taken as a result of laboratory measurements For these reasons, the quality of the results becomes essential. It has been recommended that students should participate in problem-solving activities by performing analyses that have a purpose and not perform experiments focused on showing a theoretical concept explained in a previous lecture.[2] In traditional laboratory courses, students must deliver the result of the analysis of an unknown compound without any decision being required on the basis of this result and with no greater aim or purpose than to confirm a preliminary hypothesis These results are usually obtained after measuring replicates of the same sample, and conventional statistical methods are applied to calculate the mean value and its variability. This indicates that there is a need for practical lessons implementing QC tools and critical thinking that will help students to develop the skills needed both to apply QC methods effectively and to identify and solve problems.[8,9]

Objectives

Methods

Results

Conclusion