Empirical software engineering experts on the use of students and professionals in experiments

Abstract

[Context] Controlled experiments are an important empirical method to generate and validate theories. Many software engineering experiments are conducted with students. It is often claimed that the use of students as participants in experiments comes at the cost of low external validity while using professionals does not. [Objective] We believe a deeper understanding is needed on the external validity of software engineering experiments conducted with students or with professionals. We aim to gain insight about the pros and cons of using students and professionals in experiments. [Method] We performed an unconventional, focus group approach and a follow-up survey. First, during a session at ISERN 2014, 65 empirical researchers, including the seven authors, argued and discussed the use of students in experiments with an open mind. Afterwards, we revisited the topic and elicited experts’ opinions to foster discussions. Then we derived 14 statements and asked the ISERN attendees excluding the authors, to provide their level of agreement with the statements. Finally, we analyzed the researchers’ opinions and used the findings to further discuss the statements. [Results] Our survey results showed that, in general, the respondents disagreed with us about the drawbacks of professionals. We, on the contrary, strongly believe that no population (students, professionals, or others) can be deemed better than another in absolute terms. [Conclusion] Using students as participants remains a valid simplification of reality needed in laboratory contexts. It is an effective way to advance software engineering theories and technologies but, like any other aspect of study settings, should be carefully considered during the design, execution, interpretation, and reporting of an experiment. The key is to understand which developer population portion is being represented by the participants in an experiment. Thus, a proposal for describing experimental participants is put forward.

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Notes

  1. 1.

    http://isern.iese.de/

  2. 2.

    http://softeng.polito.it/ESEIW2014/ISERN/program.html#Students

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Acknowledgements

We would like to thank all the ISERN 2014 participants for the inspiring and energetic discussions. We would like to thank both the anonymous experts and the following non-anonymous experts for participating in the survey: Paris Avgeriou, Teresa Baldassarre, Victor Basili, Giovanni Cantone, Jeff Carver, Tore Dybå, Hakan Erdogmus, Vladimir Mandic, Manuel Mastrofini, Daniel Mendez, Oscar Pastor, Guilherme Horta Travassos, Stephan Wagner, Qing Wang, Roel Wieringa, and Dietmar Winkler. We thank Sonnhild Namingha for proof reading the manuscript. This research is supported in part by the Academy of Finland Project 278354.

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Correspondence to Davide Falessi.

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Communicated by: Mark Harman

Appendix

Appendix

Invitation Letter

Dear First name Last name,

During an ISERN 2014 session, we discussed the uses of students and professionals as subjects of software engineering experiments. Afterwards, Davide Falessi, Natalia Juristo, Claes Wohlin, Burak Turhan, Jürgen Münch, Andreas Jedlitschka, and Markku Oivo revisited the topic, elicited experts’ opinions, fostered discussion, and derived some conclusions. These conclusions are currently summarized in a paper, we aim to publish in EMSE. The aim of this research is to identify pros and cons of using students and professionals in software engineering experiments. Our results aim to support researchers during generalization of results from experiments as well as reviewers during the evaluation of experiments.

As an attendee of ISERN 2014 meeting, we care about knowing your degree of agreement with the reached conclusions. We would appreciate if you could share with us your level of agreement on our conclusions. The aim of this survey is to add the community view on our conclusions. Because we care about your opinion, you should not hesitate or be afraid to disagree with our conclusions.

The survey takes approximately 10 min to be completed. Your answers will be confidential and will only be reported in an aggregated form. Reminders will be sent to non-respondents only. You will be personally acknowledged in the paper.

As a member of ISERN, please collaborate with us by participating to this survey by using this URL:

The deadline is in two weeks from now.

If you experience any troubles or you have any comment, please contact Dr. Davide Falessi at DFalessi@calpoly.edu

Best regards,

Davide Falessi, Natalia Juristo, Claes Wohlin, Burak Turhan, Jürgen Münch, Andreas Jedlitschka, Markku Oivo.

Introduction

Thank you for participating in our survey on students and professionals in software engineering experiments.

The aim of this research is to identify pros and cons of using students and professionals in software engineering experiments. Our results aim to support researchers during generalization of results from experiments as well as reviewers during the evaluation of experiments.

The survey takes approximately 10 min to be completed. Your answers will be confidential and will only be reported in an aggregated form.

If you experience any troubles or you have any comment, please contact Dr. Davide Falessi at DFalessi@calpoly.edu

Experience

  1. 1.

    What is your level of experience in performing (designing, running, analyzing, reporting) controlled experiments?

  • Expert: more than 3 published experiments

  • Novice: between 1 and 2 published experiments

  • Amateur: no published experiment or you do not know what an experiment is

Agreement

  1. 2.

    For the following statements, we would like to get your level of agreement (completely agree, partially agree, partially disagree, completely disagree, I do not know or I do not want to answer)

  2. 1.

    Experiments with students are not of lower relevance than experiments with professionals.

  3. 2.

    Experiments with students are not of less interest than experiments with professionals.

  4. 3.

    Experiments with students might exhibit lower external validity than experiments with professionals.

  5. 4.

    Internal and external validities are of equal importance.

  6. 5.

    Classifying experiment participants using a binary scale (students or professional) is an inappropriate approach.

  7. 6.

    Students participating in an experiment are a convenience sampling.

  8. 7.

    Professionals participating in an experiment are a convenient sampling.

  9. 8.

    We should think about population and validity already before conducting the experiment at the time when we are planning to use convenience sampling.

  10. 9.

    The use of students better supports the improvement of experiment design and protocol than professionals.

  11. 10.

    Conducting experiments with professionals as a first step should not be encouraged unless high sample sizes are guaranteed.

  12. 11.

    Conducting experiments with professionals entails a higher treatment conformance threat to validity than experiments with students.

  13. 12.

    Conducting experiments with professionals entails longer learning cycles than experiments with students.

  14. 13.

    Conducting experiments with professionals underestimate the positive effects of new technology than experiments with students.

  15. 14.

    The suitability and representativeness of students as proxies for professional developers change with different contexts and with different types of population.

Thank You

We appreciate the time and effort you spent in answering this survey. Please report your last name if you want to be personally acknowledged in the paper.

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Falessi, D., Juristo, N., Wohlin, C. et al. Empirical software engineering experts on the use of students and professionals in experiments. Empir Software Eng 23, 452–489 (2018). https://doi.org/10.1007/s10664-017-9523-3

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Keywords

  • Experimentation
  • Threats to validity
  • Generalization
  • Subjects of experiments
  • Participants in experiments