on purposeful sampling techniques is that they are not mutually exclusive and the researcher is advised to make a selection that enhances the prospect of obtaining information-rich cases that enable an optimal illumination of the issues pertaining to the research question(s). Patton does however concede (p. 181) that there is no perfect choice of a purposeful sampling technique and the researcher should select a technique that fits the purpose of the study, the questions that are asked and the resources that are available.
The phenomenological approach adopted for the current study necessitated the selection of respondents based on the following criteria:
The respondents must be software practitioners who have had at least 5 years of experience in software development in an organisational context;
The respondents must have at least 2 years of experience in the use of agile software development methodology or in the use of methods that are intrinsic to agile software development.
The criteria identified for the selection of respondents is aligned to the purpose of the study. The purposeful sampling used is a mix of criterion-based sampling, snowball sampling and opportunistic sampling. These purposeful sampling techniques have been described in Patton (1990, p. 183) and Given (2008, p. 697) as:
Criterion-based sampling: identifying information-rich cases that meet some criterion;
Snowball/Chain sampling: Use the identified subjects of a study as a source to obtain knowledge of cases of interest of other people who meet the criteria for the study and to continue this process iteratively;
Opportunistic sampling: The researcher makes ‘on the spot’
decisions to take advantage of new opportunities during data collection. This approach capacitates the researcher to identify new
The purposeful sampling strategies adopted in the current study consists of a hybrid of planned and unplanned data collection. The planned component (criterion-based) entails an identification of subjects who meet the set criteria for the study. Patton (1990) does however suggest that one of the strengths of purposeful sampling is the ability of the researcher to be agile and identify opportunities that may develop after fieldwork has begun. This approach permits the sample to emerge during the course of fieldwork and is aligned to the snowball and opportunistic sampling techniques.
4.2.1 Sample Size
With regards to sample size, many of the prominent authors of qualitative research methodology are of the opinion that there is a trade-off between breadth of the study and the depth of the study (Patton, 1990, p. 184). Huberman et al.
(2013) clarify this assertion by suggesting that qualitative research usually involves a small sample of people who become the focus of an in-depth study. While none of the authors venture to provide any form of quantified guidance on the sample size of a qualitative study, Creswell (2013, p. 239) suggests the following guidelines regarding the sample size for qualitative research:
In narrative research, a sample size of two would be adequate;
In phenomenological research, a sample size in the range from 3 to 10 is advocated;
In grounded theory research, a sample size of 10 to 30 is advocated;
In case study research, there should be a study of at least four to five cases.
While these guidelines apply to general qualitative research, they also have a strong resonance with a qualitative study that adopts a phenomenological approach. The preceding claim is based on the guidelines suggested by Vagle (2016) for the sample size for a phenomenological study. Basically, the researcher has two options. The study could involve spending substantial time with one or two participants over a prolonged period or spending relatively little time with ten
to fifteen participants. The choice between these alternatives is an intuitive one and is left to the discretion of the researcher. Whilst these quantification measures merely provide a set of guidelines, Creswell goes on to suggest that the data gathering exercise should continue until no new insights in the main phenomenon of the study is revealed, or a point of data saturation is achieved.
An initial sample of 12 software professionals was used for the purpose of the current study. The criteria used in the selection of the cohort of software professionals is that they should have had at least 5 years of experience in the capacity of a software developer or manager of the software development process in an organisational context and at least 2 years of experience of working in an environment where agile software development methodology (ASDM) is implemented. This criterion-driven phase was supplemented by an opportunistic phase where the researcher was able to use the initial sample as a lead onto other practitioners who met the study’s main criterion, a strategy that Huberman et al.
(2013, p. 31) refer to as “conceptually driven sequential sampling”.
The Sample Size and Selection Criteria
As Gill (2014) has suggested, the decision to opt for a phenomenological research approach is based on the imperative to search for the “essences” (P. 5) of the subjective experience of a phenomenon. Malone (2014, p. 42) reinforces the preceding suggestion by commenting that phenomenology “…places a primacy over participant’s experience over established theory”. Hence the reliance on purposive sampling is crucial because it allows the researcher an opportunity to select participants who can offer a rich insight into the phenomenon of the study.
With regards to the choice of samples size, guidance is obtained from a seminal paper on sample size selection for a PhD study that uses the phenomenological approach by Mason (2010). The essence of this study is to provide knowledge of previous studies that have used phenomenology successfully. In the context of a phenomenological study, success alludes to the potential for the study to obtain data saturation (no new information emanates from the study’s respondents) as early as possible. According to Malone, 68% of the phenomenological studies
successfully used a sample size that ranged from 5 to 25. With reference to the current the choice of sample of 16 falls well within this range.
With regards to the level of experience of the respondents for the study, guidance is obtained from a study by Malone (2014). In this study, Malone used phenomenology to ascertain the experiences of Scrum Masters when it comes to adaptation of Scrum methodology in an organisational context. In this study, the average number of years of experience by the respondents was 4.7 years. Although Malone prescribed the minimum number of years of experience as 1, much of the information rich data was generated by respondents who had in excess of 2 years of experience. It was also established that the more experienced respondents (between 2 and 5 years) provided greater insight into the adaptation of Scrum methodology. Aligned to this outcome, the current study prescribed a minimum of 5 years of experience of working in the domain of general software development and 2 years of experience in the domain of agile software development. These specifications fall within the parameters reported in the Malone study that provided information rich data and enhanced the prospect of data saturation.