Pre-service Physics Teachers' Difficulties in Evaluating Experimental Evidence

The reported research is about the difficulties that pre-service physics teachers experience when they judge the quality of experimental results to draw conclusions. Thirty-six pre-service physics teachers participated in the study, enrolled in six semesters (six participants in each semester). They designed, conducted experiments, analyzed the results, evaluated the quality of experimental evidence and finally, evaluated the whole experimental procedure. In addition, the participants were provided with experimental results not collected by themselves (secondary sources data) and were asked to judge the quality of collected evidence and conclusions. Data sources include laboratory reports for each experiment and exam papers, supplemented with individual interviews. A qualitative and quantitative data analysis identified trends within the participants. Findings show that pre-service physics teachers have difficulties with the concepts of experimental validity, measurement reliability, accuracy and precision. Furthermore, they have difficulties in putting such concepts together to judge how well they can rely upon evidence to draw conclusions. The participants also demonstrate difficulties with sources of experimental errors and do not make the distinction between random and systematic errors. In particular, they are confused when they reason about what it is that "gets better" when one takes repeated measurements. It is argued that there is a need for specialized programmes of teacher education to address the development of laboratory skills (i.e. evaluation of experimental evidence) so that pre-service teachers become confident in teaching in the physics laboratory in secondary schools. Implications for teaching practice, curriculum development and further research have been discussed.