A research design describes the methods and steps a researcher follows in gathering information about a study (McMillan & Schumacher, 2010, p. 20). It is the overall strategy that one chooses to link the different components of a research study in a comprehensible and logical manner to ensure that a research problem is addressed. It therefore includes, method of data collection, measured and analysed. This study employs a descriptive research study design.
Yin suggested three types of descriptive research study designs, namely observational, case study and survey. However, the case study research design was chosen for this study as this design is used to perform an in-depth study of an individual or group of individuals which may involve both qualitative and quantitative research methods (Jackson, 2015; Kessler & Stafford, 2008). The emphasis is on the fact that a case study research could be used for an individual, organization, event or
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action at a time (Kessler & Stafford, 2008). Jackson (2015) further indicated that the case study allows for the study of a rare phenomenon but cannot be used for accurate prediction since it could occasionally be biased.
Yin (1994, p. 23) defined a case study research design to be an empirical inquiry that investigates a contemporary phenomenon within its real-life context when the boundaries between phenomenon and context are not clear and in which multiple sources of evidence are used. Nevertheless, Yin's definition fits this study in two respects; first, empirical evidence of teachers' knowledge in PBL was collected using a questionnaire and secondly, information on teachers as the context of the study was obtained at school (phenomenon within its real-life context).
In another view, Yin (1994) indicated that case studies are the preferred strategy when ‘how’ and ‘why’ questions are posed (explanatory case study). This makes it possible to study the second sub-question ‘How do these physics teachers implement PBL in their classrooms? This was done using the case study design since it was posed using ‘how’. Moreover, after deciding on a case study approach, it is important for a researcher to determine which type of case study to use in a research. There are two types of case study design, namely exploratory and explanatory case study (Yin, 2003). Yin (2003) noted that the choice of case study method depends on three things:
1. the type of research question posed;
2. the control a researcher has over actual behavioural events; and 3. The degree of focus on contemporary as opposed to historical events.
Consequently Yin (2003) described an exploratory research as dealing with a situation where a researcher has an idea or must observe something and wants to find out more about it (Yin, 2003). In other words, he explained that exploratory research design is used for a problem that has not been studied clearly. Moreover, he indicated that the exploratory case study design is employed as a research design if the research question focuses on ‘what’. In a similar view, Saunder, Lewis, and Thornhill (2012) described exploratory case study design as a research technique used to study a new topic or a study in a new dimension and does not intend to offer conclusive evidence. They further indicated that it helps to have a better understanding of the problem.
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Generally, it is the case in this study, which is aimed at making teachers aware of an alternative approach to teaching physics and to influence them to use it in their teaching.
On the other hand, explanatory research is meant to explain why events occur in order to build, elaborate on, extend or test the theory. Yin (2003) put forward that ‘how’ and ‘why’ questions are explanatory, and are likely to favour case studies, experiments or histories.
Nevertheless, it could be noted from the previous explanations that in this study a combination of descriptive case study design and exploratory case study design were used. However, this could be viewed from two different perspectives; the main research question for this study is ‘what are the experiences of physics teachers when implementing problem-based learning?’ This question was posed with ‘what’ and therefore is exploratory and favours any of the research strategies (survey, case studies, experiments or histories) (Yin, 2003). Again, the two sub-research questions: ‘What are physics teachers' experiences of the use of PBL before an intervention?’ and ‘What are the successes and challenges of these physics teachers when using PBL in their classrooms’ were posed using ‘what’ and are also exploratory.
In addition, Shields and Rangarjan (2013) held the contrary view and explained that the exploratory case study relies on methods such as informal qualitative approach through discussions and formal qualitative research through in-depth studies. Nevertheless, in this study, qualitative data were collected with open-ended questionnaires, interviews and lesson observations while quantitative data were obtained from the biographical data from respondents. Johnson and Christensen (2008, p. 328) argued that in a quantitative non-experimental design there is no control of conditions, variables and extraneous influences. In this study teachers' biographical data were studied using the non-experimental design but the actual study was done using a qualitative data collection and analysis technique since the study focuses on obtaining information about the experiences of some groups of teachers and not studying the relationship between variables.
Consequently, since the study collected data using two research techniques, one following the other, the exploratory design was considered the best approach. This
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was based on Cresswell’s (2002) argument that the exploratory design is recommended if the researcher’s aim is to collect quantitative and qualitative data in sequence in a form of a mixed approach. Cresswell (2002) pointed out that the mixed- methods approach has the advantage of yielding detail information about a study, as opposed to a single approach.
As a result of the argument above, the exploratory case study research design was employed in this study since the research questions were posed with ‘what' and the study covers a small geographical location and deals with issues regarding education (Gulsecen & Kubat, 2006). Gulsecen and Kubat (2006) advanced that the case study research design is the preferred approach when the study covers a small geographical location and deals with issues regarding education.