Route C: Extension

All approaches within Route C: Extension will involve some form of change to the research method used in your main journal article, or at the very least, the measures used within those research methods (e.g., the questions used within a questionnaire to measure a particular construct or variable). However, dissertations guided by a design-based extension, or method or measurement-driven extension, are likely to require considerably more changes to the research methods and measures compared to population or context/setting-driven extensions:

Population and context/setting-driven extensions

Just like when following a population or context/setting-based generalisation, there are similar practical reasons why it may not be possible for you to use the same research method in the main journal article in your dissertation (e.g., problems of access, timeframe and cost), as discussed previously. However, for the most part, population or context/setting-driven extensions require changes to the measures used within the research methods (e.g., the questions in the survey or the observation points in the structured observation) that were applied in the main journal article when studying the new population or context/setting in your dissertation. This is necessary because population or context/setting-driven extensions require you to add, modify or omit certain constructs and/or variables from the original study to reflect the differences in the characteristics of the new population or context/setting that you are studying. Adding, modifying or omitting constructs and/or variables within the research methods you use goes a lot further than simply rewording measures, which is all that is often required under Route B: Generalisation.

Method and measurement-driven extensions

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. You can learn more about construct validity and these types of bias in the article, Construct validity, in the Research Quality section of the Fundamentals part of Lærd Dissertation.

The most obvious impact of such method or measurement-driven extensions for the research methods you use in your dissertation is that you would have to either use a completely different research method from the one applied in the main journal article, or use multiple research methods (i.e., in the case of mono-method bias) and/or add, modify or omit certain measures within the research method used in the main journal article (i.e., in the case of mono-operation bias). If you are changing the research method entirely, or using multiple research methods (i.e., one of the research methods used is likely to be the one applied in the main journal article), you should evaluate the relative strengths and weaknesses of alternative research methods in the Research Methods section of the Fundamentals part of Lærd Dissertation, in order to be able to justify your choice of research method. In addition, look to the literature you used in the section, Route C: Extension, within STEP THREE: Use the literature to explain and justify the route you have chosen, and the approach within that route, in STAGE FIVE: Building the theoretical case. This should help you to identify the mono-method bias in the research method used in the main journal article, which led to your decision to either change the research method being used in your dissertation entirely, or add a second research method. This section of STAGE FIVE: Building the theoretical case is equally useful in order to identify the mono-operation bias in the measures used in the research method applied in the main journal article, which have led you to add, modify or omit such measures in your dissertation.

Final thoughts

Before moving on to STEP FOUR: Sampling strategy, make sure that you know which research method(s) you are going to use in your dissertation because your research methods, just like your research design, affect your sampling strategy, and in particular, the sampling techniques that you use.