Case Selection Strategy

Once the general definition of the case study has been established, sampling becomes critical. From the outset, it is important to realise that sampling is not a process that should be solely associated with the logic derived from statistical and mathematical probability (Mason, 1996). Indeed, a case study demands the logic of purposeful sampling as opposed to random sampling. Unlike statistical sampling, where the emphasis is on having a representative sample that is used to substantiate findings to the wider environment , purposeful sampling is concerned with selecting information-rich

cases whose study will illuminate the question under enquiry, hence, the term purposeful sampling (Miles and Huberman, 1994). In general terms, this form of sampling consists of the “procedures used to identify, choose, and gain access to relevant units which will be used for data generation by any method” (Mason, 1996).

The selection of cases represents the first important element of the sampling process. The literature provides a wide range of sampling strategies that researchers could utilise to select their cases (see table 5), however, regardless of whichever strategy is used, “the underlying principle that is common to all these strategies is selecting information rich cases” that will allow them develop theory (Patton, 1990).

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In essence, they are cases worthy of in-depth study. The sampling strategy that best fits the purpose of this research, the resources available, the question being asked, and the constraints being face, is criterion sampling. The justification for adopting this sampling approach was grounded in a number of rationales. First, to be sure that each cases was likely to be information rich, it was critical that each case company engaged in product development, had control over the product development process and were open to hosting discussion on the consideration of management of the external-internal affordance relationship within their product’s development process with the researcher.

Second, in order to achieve the objectives of this research, each case company had to have delivered to the market a range of product offerings that were deemed to have successfully afforded, over time, utility requirements of specific product use environments.

Thirdly, each company’s range of product offering were required to be use environment driven product development example, which exhibited specific external product-user interaction requirements and could also be identified as comprising distinct utility functions that were derived of action possibilities that resulted of the internal configuration’s interactive arrangement. Additionally, this range of product offerings had to have been subject to phases of improvement that refined or amended the standard design of the product’s affordance, relative to which a retrospective review of management of the external-internal affordance relationship process could be explored. Fourth, due to resources and the purpose of the research (multiple site visits required), only companies located in Ireland could be included in the analysis.

Obviously, these pre-established criteria have implications for the next sampling issue, that is, how many cases are needed? According to Voss (2009), “the fewer the case study, the greater the opportunity for depth of observation”. Single cases are ideal for longitudinal studies but have limitations such as limited generalizability of the conclusion and misjudgement of a single phenonenon. However, when a phenomenon is compared across cases, it offers a solution to these limitations as it works towards strengthening external validity and attempting to prevent observer bias. Multiple cases are suggested to increase the methodological rigor of the study through "strengthening the precision, the validity and stability of the findings," (Miles and Huberman, 1994), particularly,

because "evidence from multiple cases is often considered more compelling (Yin, 1994). For this reason, the reseacher decided to opt for multiple case studies. Two cases were decided upon as the appropriate number of cases, and a retrospective case approach was taken as retrospective cases allow for more controlled case selection.

According to Voss (2009), theory building through case research requires case selection to be made using replication logic rather than sampling logic: that case selection should predict similar results (a literal replication) or produces contrary results but for predictable reasons (theoretical replication). Yin, (1998) distinguishes between literal replication (where the cases are designed to corroborate each other) and theoretical replication (where the cases are designed to cover different theoretical conditions). Informing case choice was literal replication based upon Maier & Fadels (2009, 2007) categorisation of affordance subsystems and that defined internal and external contextual focuses of product affordance design.

The rationale behind using a two case study design was twofold.

Firstly, as previously mentioned, the criterion of investigating the research phenomenon reflected controlled selections that enabled exploration of how improvements in the complementarity of action possibilities, resulting of the re-design of subsystem aspects (external and internal artefact to use and artefact to artefact interaction requirements) of the existing product’s design, was approached and the realisation of a utility offering deemed complementary to a use environment realised. A minimum of two cases were necessary to collate case observations of the approaches adopted to management of the external-internal affordance relationship, and to support consolidated observations through a compare and contrast of improvement project and process insights across the two cases. Both case’s improvement process examples were conducted on complex products that provided rich insights and represented a saturation of sampling criterion. Secondly, since the research is pragmatic (due to the contextual nature of improving through subsystem re-design), it has a focus on understanding rather than generalisability (Hirshman, 1986). Thus, the use of two cases is also more applicable for allowing the researcher to give more in-depth and detailed attention to exploring the research phenomenon.

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Finally, before leaving this discussion on sampling, it is worth noting, that in practice, decisions regarding the selection of cases and the appropriate number of sample units that are needed, is largely dependent upon practical issues, such as, the possibility of gaining access (de Weer-Nederhof, 2001). Indeed, numerous potential companies were contacted; some refused to participate in the research, while other failed to satisfy the pre-established criteria.

The specific products selected were a headphone and a pacemaker IPG device. Case selection criteria were deemed saturated at the point where the case’s improvement project examples enabled the process to managing the external-internal relationship to be determined through insights on the product re-development actions in two different companies. Table 6 presents an overview of the cases selected. Case 1, a headphone product improvement process and case 2, a pacemaker IPG product improvement process are developed through a total of five improvement project examples and two company perspectives on the process to managing the external-internal relationship.

The External-internal Relationship of Managing:

Case 1 Case 2

Headphone Affordance Improvements Pacemaker IPG Affordance Improvements Number of Improvement

projects Explored within 3 2

Table 6 Sampling Criterion

Case 1 was selected, research was carried out and the case written up before the second case company was selected. To facilitate direct replication, insights from case 1, illustrated within table 7, updated the selection criteria for case 2.

Case 1 Insights Case 1 Company A External Subsystem Focus Internal Subsystem Focus Knock- on Effects Transferrable for Future Use

Improvement Project 1  

Improvement Project 2  

Improvement Project 3   

Table 7 Case 1 Insights Shaping Case 2 Selection Criteria

Case 1 provided insights on the process to implementing three improvement project examples. One project provided rich insights on improvements in the complementarity of an external subsystem. The other two improvement projects provided rich insights on improvements in the complementarity of two internal subsystems. A knock-on effect was observed in one improvement project and all three improvement projects resulted in transferrable design data useful in subsequent company A improvement projects.

In addition to the pre-stated selection criteria, the second case company was required to provide insights on the process to improving the complementarity of external and internal subsystems parts, provide insights on how knock-on effects were prevented or resolved and insights on transferrable design data useful in subsequent improvement projects.

As illustrated within table 8, case 2 provided insights through two improvement project examples. Case 2 Insights Case 2 Company B External Subsystem Focus Internal Subsystem Focus Knock- on Effects Transferrable for Future Use

Improvement Project 1  

Improvement Project 2   

Table 8 Case 2 Insights supporting Direct Replication with Case 1

One project provided rich insights on the process to implementing improvements in the complementarity of an external subsystem. The other provided rich insights on the process to implementing improvements in the complementarity of an internal subsystem. One improvement project provided insights on how knock-on effects were prevented. Finally, both improvement projects provided insights on transferrable design data useful in subsequent company B improvement projects.

These five improvement project examples enabled exploration of the process to managing the external-internal relationship in both case companies. Consequently, the point of saturation was deemed reached through the five improvement process examples of the two case studies.