Table 2 The chosen framework for content analysis

1. Driving question

• Features of a good driving question in STEM PBL (Hasni et al., 2016):

1. The driving question has an authentic link to the real world experienced by the learners.

a. Learning environments are local or otherwise familiar to students.

b. Use of socio-scientific issues.

2. The driving question is open-ended.

• Authenticity can also be demonstrated by having students participate in using scientific practices (Hasni et al., 2016). However, this was studied under ‘3. Scientific practices’. Additionally, due to the level of detail in the studied materials, ‘familiar or local learning environments’ were considered in the wider sense of the term.

• The third feature of a good driving question, “The driving question creates the need to understand the central scientific concepts related to the studied subject” (Hasni et al., 2016), was not included. This was due to the studied projects being from different countries, and examining the projects in relation to the different curricula would have been out of the scope of this study.

2. Learning goals

• Learning goals stated by students and teachers:

a. Practical goals

b. Goals with a reference to students’ development

• Learning gains stated by students and teachers

• Since the international sample of the study did not allow a direct comparison between the projects and the national curricula, the two main aspects of this key characteristic were chosen as the focus: did the teachers or students report any learning goals that were set for the project, and did they report any learning that happened as a result of the project?

3. Scientific practices

1. Conceptualisation:

a. presenting research questions

b. presenting hypotheses

2. Investigation:

a. exploration (if there is only a research question but no hypothesis)

b. experimentation (if there is a hypothesis)

c. data interpretation.

3. Conclusions.

4. Discussion:

a. communicating the results

b. reflection

• Scientific practices were studied through the phases of inquiry-based learning, as they describe the scientific practices that students carry out in practice within one research project (Pedaste et al., 2015).

• First phase, ‘orientation’, was left out as its outcome, the driving question, is studied separately.

• Many models developed for evaluating the quality of inquiry-based learning can be adapted for PBL (Thys et al., 2016). Also, for example, Mentzer et al. (2017) studied how teachers implemented the phases of inquiry-based learning in their PBL unit plans.

4. Collaboration

• Collaboration between students

• Collaboration between teachers

• Collaboration with partners from outside of the school

• These categories arose from the materials.

5. Using technological tools

• ICT (information and communication technologies).

• Technology that was used as a scientific research tool.

• These categories arose from the materials.

6. Creating an artefact

• The same question/problem is answered to with multiple artefacts.

• Multiple single artefacts from separate activities.

• One clear artefact.

• A larger artefact that includes the smaller ones.

• These categories arose from the materials.

• Krajcik & Shin (2014) outline that the artefact should answer the driving question, reveal the students’ level of understanding, and support students in gaining an understanding about the topic. These would have been useful categories, however it was not possible to use them in this study due to the lack of driving questions and detail about the aims of the projects.