Crossover Designs in Software Engineering Experiments: Benefits and Perils
Abstract
In experiments with crossover design subjects apply more than one treatment. Crossover designs are widespread in software engineering experimentation: they require fewer subjects and control the variability among subjects. However, some researchers disapprove of crossover designs. The main criticisms are: the carryover threat and its troublesome analysis. Carryover is the persistence of the effect of one treatment when another treatment is applied later. It may invalidate the results of an experiment. Additionally, crossover designs are often not properly designed and/or analysed, limiting the validity of the results. In this paper, we aim to make SE researchers aware of the perils of crossover experiments and provide risk avoidance good practices. We study how another discipline (medicine) runs crossover experiments. We review the SE literature and discuss which good practices tend not to be adhered to, giving advice on how they should be applied in SE experiments. We illustrate the concepts discussed analysing a crossover experiment that we have run. We conclude that crossover experiments can yield valid results, provided they are properly designed and analysed, and that, if correctly addressed, carryover is no worse than other validity threats.
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The period at which a participant reviewed a particular AOI can potentially affect participants' behavior through a maturation or exhaustion effect, making it necessary to condition on it to avoid bias.
“In our study, for example, the period (at what time a participant reviewed a particular AOI) can potentially affect participants' behavior in what is called the maturation or exhaustion effect [18], making it necessary to condition on it to avoid bias.”
From Same Scrutiny, More Time: Eye Tracking Insights into Reviewing LLM-Labelled Code (2026) · cites this paper as [18]
The crossover design induces threats to internal validity [18], such as the learning effect over multiple periods or an optimal sequence effect.
“The crossover design induces threats to internal validity [18], e.g., the learning effect over multiple periods or an optimal sequence effect.”
From Same Scrutiny, More Time: Eye Tracking Insights into Reviewing LLM-Labelled Code (2026) · cites this paper as [18]
We mitigate crossover-design threats by adjusting for them in our analyses [18], [44], which factors out effects from the phenomenon of interest and allows us to determine that they did not affect our experiment.
“We mitigate these by adjusting for them in our analyses [18], [44], which not only factors out the effects from the phenomenon of interest but also allows us to determine that they did not affect our experiment.”
From Same Scrutiny, More Time: Eye Tracking Insights into Reviewing LLM-Labelled Code (2026) · cites this paper as [18]
Cites
Experimentation in Software Engineering
Wohlin, C., Runeson, P., Höst, M., Ohlsson, M. C., Regnell, B., & Wesslén, A. (2012) · doi:10.1007/978-3-642-29044-2 · Cited by 4,460 · see citing works
Ellis, P. D. (2010) · doi:10.1017/cbo9780511761676 · Cited by 2,461 · see citing works
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Effect sizes and their variance for AB/BA crossover design studies
Madeyski, L., & Kitchenham, B. (2018) · Empirical Software Engineering · doi:10.1007/s10664-017-9574-5 · Cited by 38 · see citing works
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Baldassarre, M. T., Caivano, D., Fucci, D., Juristo, N., Romano, S., Scanniello, G., & Turhan, B. (2021) · Journal of Systems and Software · doi:10.1016/j.jss.2021.110937 · Cited by 15 · see citing works
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Baldassarre, M. T., Caivano, D., Fucci, D., Romano, S., & Scanniello, G. (2022) · Journal of Systems and Software · doi:10.1016/j.jss.2021.111154 · Cited by 9 · see citing works
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Guglielmi, E., Arnoudova, V., Bavota, G., Oliveto, R., & Scalabrino, S. (2025) · arXiv · doi:10.48550/arxiv.2504.06808 · Cited by 1 · see citing works
“We will also conduct statistical tests for carryover effects to ensure validity of our findings [28], [29].”
Same Scrutiny, More Time: Eye Tracking Insights into Reviewing LLM-Labelled Code
Khojah, R., Gomes de Oliveira Neto, F., Mohamad, M., Frattini, J., & Leitner, P. (2026) · Proceedings of the 41st IEEE/ACM International Conference on Automated Software Engineering · doi:10.1145/3832783.3834423
- Authors
- Vegas, S., Apa, C., & Juristo, N.
- ORCID
- Vegas, Sira
- Venue
- IEEE Transactions on Software Engineering
- Published
- 2016-02-01
- Volume
- 42
- Issue
- 2
- Pages
- 120-135
- ISSN
- 0098-5589 (ISSN-L)
- 1939-3520
- OpenAlex
- W2295373235
- Cited by
- 145
- References
- 2
- Citations by year
- 2026: 11 · 2025: 19 · 2024: 16 · 2023: 19 · 2022: 16 · 2021: 19 · 2020: 14 · 2019: 13 · 2018: 9 · 2017: 6 · 2016: 3
- FWCI
- 16.18
- Type
- journal article
- Language
- en
- Open access
- closed
- Locations
- IEEE Transactions on Software Engineering (publishedVersion)
- Funders
- Spanish Ministry of Economy and Competitiveness research (TIN2011-23216)
- Topics
- Physical Sciences › Computer Science › Information Systems › Software Engineering Techniques and Practices
- Social Sciences › Decision Sciences › Management Science and Operations Research › Optimal Experimental Design Methods
- Physical Sciences › Computer Science › Artificial Intelligence › Advanced Software Engineering Methodologies
- Keywords
- crossover design, software engineering experiments, residual effects, experimental design, threats to validity, experimental analysis, best practices, research methodology
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