A topic in research methodology
Introduction
In an experiment, researchers look to see if a 'treatment' (such as a new teaching resource, or an innovative pedagogy) brings about a change – such as an increase in knowledge, a change of understanding, or a modification of views.
However, as many things might bring about such a change (especially when the study takes place over a topic, course unit, term of even longer) it is important to have a control.
Read about confounding variables
In true experiments the 'units of analysis' (classes, learners, schools, etc.) are randomly assigned to the experimental treatment or the control.
Read about control conditions in experimental research
Comparisons in quasi-experiments
However, in education many studies (quasi-experiments, natural experiments) are not able to randomise in this way, and comparisons have to be found that are considered near enough equivalent with the experimental group in relevant characteristics as is possible. This is always a key feature of such studies as it is unlikely two such groups can every be completely equivalent, and researchers may not be aware of the variables which might make a difference. Researchers need to make a case that their comparison group is a suitable standard for comparison.
Read about testing for initial equivalence
Examples:
| Experimental group/treatment | Comparison group/treatment | Note | Reference |
| Students in the final year of a 4 year degree preparing them for chemistry teaching Lin & Chen introduced historical case studies and wanted to see if this changed students' conceptions of the nature of science | Students in the 'junior'(3rd) year of the same 4 year degree preparing them for chemistry teaching No historical teaching (The authors argued that the extra year of study should not itself be a factor in student conceptions of the nature of science) | The researchers were interested in whether historical cases have any educational value (level 1 comparison), so compared a specific educational input with a condition without that input. | Lin, H.-s., & Chen, C.-C. (2002). Promoting preservice chemistry teachers' understanding about the nature of science through history. Journal of Research in Science Teaching, 39(9), 773-792. https://doi.org/https://doi.org/10.1002/tea.10045 |
| School children attending a residential Malay school, taught a topic using DARTs pedagogy through 5 half-hour lessons | School children in the same grade attending a different residential Malay school, taught the same topic using laboratory work through 3 half-hour lessons | The researchers were trying two see if DARTs pedagogy was more effective than laboratory teaching (level 2 comparison) (Read more about this study) | Shamsulbahri, M. M., & Zulkiply, N. (2021). Examining the effect of directed activity related to texts (DARTs) and gender on student achievement in qualitative analysis in chemistry. Malaysian Journal of Learning and Instruction, 18(1), 157-181. https://doi.org/10.32890/mjli2021.18.1.7 |
Work cited:
- Taber, K. S. (2019). Experimental research into teaching innovations: responding to methodological and ethical challenges. Studies in Science Education. doi:10.1080/03057267.2019.1658058 [Download this article]
