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

摘要

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.