Route C: Extension

In many respects, Route C: Extension is more than just replication because the changes you make to components of the main journal article, such as the research design, constructs/variables, methods and measurement procedures, and data analysis approach adds a great deal more originality and independent thought to the traditional replication routes (i.e., compared with Route A: Duplication, and even Route B: Generalisation). Although all aspects of the critical literature review process are important, the focus on making substantial changes in extending the main journal article mean that you need to spend a lot more time searching the literature to explain and justify the theoretical components of your Route C: Extension dissertation. Where you focus this literature search will depend on the type of extension you take on (i.e., your approach within Route C: Extension):

• Population and context-driven extension

  If you are pursuing a population or context-driven extension (i.e., Route C: Extension), you'll know that this is similar in nature to population or context-driven generalisations (i.e., Route B: Generalisation), albeit requiring you to add, modify or omit certain constructs/variables used in the main journal article. There are a number of reasons why you may choose to add, modify or omit certain constructs/variables. To recap, let's look at Study #1 below:

• Study #1
  How salespeople build quality relationships by Boles, Johnson, & Barksdale (2000)
  Boles et al. (2000) replicated a study by Crosby et al. (1990) that examined the factors that affected relationship quality between a business customer and a salesperson, as well as the impact of such relationship quality (i.e., the antecedents and consequences of the buyer-seller relationship quality). However, Crosby et al.'s (1990) original study focused on retail customers, not business customers. Therefore, whilst replicating much of their study, Boles et al. (2000) added another construct, equity, which they felt would affect relationship quality in a business context, as opposed to a retail/consumer context. In the event, Boles et al. (2000) used three variables, previously developed by Oliver and Swan (1989) in another study to measure equity.

  This highlights that if you are choosing to extend the main journal article by applying it to a new population or context/setting, you may need to add new constructs/variables. Sometimes you can draw on previous studies to do this. Other times you will have to create them from scratch (NOTE: We show you how to do this later). Sometimes, it will not be a desire to apply the main journal article to a new population or context/setting, but the publication of new research that suggests that other constructs/variables play a role in explaining the phenomenon you are interested in. However, if no research has examined the role that these constructs/variables play within the context of the main journal article, you have a chance to extend the theoretical model that is being investigated by adding new constructs/variables. We explain about theoretical models in STEP FOUR: Set the theoretical model for your dissertation. Going back to Study #1:

  Study #1 (continued)
  Bowles et al. (2000) also found that they needed to modify some of the existing variables that were used by Crosby et al. (1990) to measure the constructs that were being studied. In other words, the constructs were the same, but the variables used to measure these constructs had to be changed in order that they were applicable to the new audience (i.e., in practical terms, the questions in the survey had to be re-worded so that they were appropriate in a business context). Furthermore, the change in context meant that some variables were no longer relevant, so these were simply omitted from the survey (i.e., these questions were deleted from the survey).

  In the case of Study #1, variables were modified or omitted compared to the main journal article because they were no longer relevant in the new population/context to which the authors wanted to make generalisations. However, such modifications may also have to be made because constructs, and the variables that are used to measure them, are constantly changing. This is because new research regularly emerges that suggests, for example, that a single construct (e.g., organisational commitment) is now thought to be made up of three broader constructs (e.g., normative commitment, continuance commitment and affective commitment); or new research provides a better (i.e., more reliable) way to measure a given construct (i.e., more reliable variables to measure a given construct emerge from other research). As a result, whilst maintaining many aspects of the original study, you may need to change some of the constructs/variables that were originally used, even if these original constructs were thought to be reliable at the time.

  Irrespective of whether you are adding, modifying or omitting constructs/variables, you need to use the literature to explain and justify such decisions. For example, you can use the literature to explain how: (a) one or more of the constructs/variables used in the main journal article is no longer relevant to the new population or context you are studying; (b) more construct valid constructs have emerged since the main journal article was published, or have been available for a longer period of time, but were not used in the main journal article; (c) more reliable ways to measure such constructs/variables are available, which need to be incorporate into your dissertation. In all three of these cases, review articles can be the best way to (a) identify ways in which constructs/variables need to be changed, and (b) justify such changes. In some cases, the extension that you have made to the main journal article will require the development of new constructs/variables, but we leave the explanation of how to do this for STAGE SIX: Setting your research strategy. If you feel that you need to learn more about reliability and construct validity at this stage in order to help you understand why you may want to add, modify or omit constructs/variables and the implications of doing so, it is worth reading our guides on Reliability and Construct validity in the Fundamentals part of Lærd Dissertation.

• Method and measurement-driven extension

  If you are pursuing a method or measurement-driven extension, you'll know that the reasons for choosing such an extension include: (a) the fact that a single measure of a construct (i.e., a single variable) was used in the main journal article, which could have resulted in mono-operation bias, such that you feel that multiple measures are required to improve the construct validity of the measurement procedure; or (b) the fact that a single or inferior method to measure a construct was used in the main journal article, which you felt could have resulted in mono-method bias, such that more than one method or a different method would improve the construct validity of the measurement procedure. If you feel unclear about these aspects of Route C: Extension or the idea of construct validity, you may want to first revisit the introductory article, Route #1: Getting started, before moving on to our guide on Construct validity in the Fundamentals part of Lærd Dissertation.
  
  Explaining and justifying a change in the method or measurement from the main journal article in your dissertation is achieved by looking to (a) the main journal article, (b) research methods theory, and (c) the literature:

• The main journal article

  Criticisms of the main journal article, whether identified by the authors of the journal article, other scholars, or during your analysis of the main journal article and broader literature, can provide a basis for using the literature to explain and justify the use of new methods or measurement procedures. For example, the measurement procedure (e.g., a survey) may have been criticised because it was not particularly reliable (e.g., it did not receive a sufficiently high Cronbach's alpha score). While you may have identified such justifications for your method or measurement-driven extension during STEP TWO: Critically evaluate the main journal article and its component parts, towards the start of this stage (i.e., STAGE FIVE: Building the theoretical case), these may also become more apparent in the next stage (i.e., STAGE SIX: Setting your research strategy) or from the Data Analysis section of the Fundamentals part of Lærd Dissertation.

• Research methods theory

  Research methods theory is a useful place to look for justifications for method-driven extensions because such theory typically explains the advantages and disadvantages of using particular research methods, as well as the relative advantages and disadvantages of using one research method (e.g., structured observation) over another (e.g., structured interviews). You can learn about such advantages and disadvantages in the Research Methods section of the Fundamentals part of Lærd Dissertation.

• The literature

  The broader literature can provide some of the strongest justifications for your method or measurement-driven extension because there are often journal articles that review and critique the use of particular research methods or measures for a given construct (e.g., a construct such as organizational commitment). These review articles are different from the broader review articles we discussed in STEP ONE (i.e., Understand the broader literature within which your main journal article and chosen route fit) because rather than reviewing and critiquing the various theoretical components used to understand a particular sub-field or construct, they focus on the research methods or measures for a given construct. As a result, they will often compare the various research methods or measures used in the literature for a given construct, explaining the various strengths and weaknesses of the different method and measurement-based approaches. Since these journal articles are construct-specific, using such journal articles to justify your method or measurement-driven extension is better than relying on the more general statements about the advantages and disadvantages of using particular research methods or measures that are presented in research methods theory (i.e., the previous bullet point).

  You will usually be able to find such journal articles, or ones that will help, by looking at the relevant section within the broader review articles we discussed in STEP ONE. After all, as we discussed in STEP ONE, these broader review articles generally discuss: (a) the use of definitions; (b) perspectives or dimensions; (c) antecedents of a construct or sub-field; (d) measurement procedures (i.e., research methods) and measures; and (e) conceptual frameworks. Within the section on measurement procedures and measures, look to the in-text citations used and the corresponding references in the reference list. There is a good chance that these journal articles will go into much more depth about the advantages and disadvantages of various measurement procedures and measures for the construct(s) you are interested in, or at the very least, give you a much better understanding of particular measurement procedures and measures (i.e., most of these in-text citations will probably refer to journal articles that focus on a particular measurement procedure or measure for a given construct, but one or two may be review articles of the major measurement procedures and measures for a given construct, which will be most helpful).

When taking on Route C: Extension, you should also search the literature to see whether your main journal article has already been extended in some way, as well as recognize whether your main journal article is, in fact, an extension of another study (e.g., your main journal article may have taken a well-known measurement procedure, such as the SERVQUAL questionnaire used to measure the construct, service quality, in order to examine service quality amongst business customers in a bank, whilst your dissertation aims to use the SERVQUAL questionnaire to measure service quality amongst retail customers in an online auction site; i.e., both the main journal article and your dissertation will have built on the initial journal article that introduced the SERVQUAL questionnaire for measuring service quality). Identify such research is important irrespective of the approach that you take within Route C: Extension. You should be able to find such research by looking closely at the introduction, literature review, research strategy or reference list of your main journal article, which are likely to mention similar research.