Muestreo teórico

Introduction
Grounded theory refers to theory developed inductively from data. It takes a case and results in a theory which fits one dataset. It explains the collected data through a middle-range theoretical framework (Charmaz, 2000). The grounded theory approach consists of a set of steps and processes which are the building blocks of a quality grounded theory. Grounded theory uses categoriesdrawn from respondents and focuses on making implicit belief systems explicit.
Grounded theory
According to Strauss and Corbin (1990) a theory is a set of relationships that proposes a reasonable explanation of the phenomenon under study. Morse (1994) extends this explanation suggesting that a theory offers "the best comprehensive, coherent and simplest model for linking diverse and unrelatedfacts in a useful and pragmatic way" (p.25). It is a way of enlightening the clear, the implicit, the unrecognised and the unknown. Theorising is the process of creating alternative explanations until a 'best fit' which explains the data most simply is obtained. This involves asking questions of the data which will create links to established theory (Goulding, 1999). Indeed, a theory is "a set ofwell-developed categories (eg, themes, concepts) that are systematically interrelated through statements of relationship to form a theoretical framework that explains some relevant social, psychological, educational, nursing or other phenomenon" (Strauss & Corbin, 1998, p.22).
Grounded theory was introduced by Glaser and Strauss in their 1967 book, The Discovery of Grounded Theory. The bookwas based on a justification for using qualitative research to build up theoretical analysis. As Goulding (1999) mentions, it was written in part as an objection against what the authors viewed as a rather passive acceptance that all the 'great' theories had been discovered and that the role of research lay in testing these theories through quantitative 'scientific' procedures.
What Glaser andStrauss suggested as grounded theory is actually a "systematic, qualitative process used to generate a theory that explains, at a broad conceptual level, a process, an action, or interaction about a substantive topic" (Creswell, 2002, p.439). It is a qualitative methodology which obtains its name from the practice of generating theory from research which is 'grounded' in data (Babchuk, 1997). It canbe defined as a method for analysing data which is most commonly used on naturalistic field data but has also been used to analyse historical and documentary data (Star, 1998). The grounded theory approach uses a "systematic set of procedures to develop an inductively derived grounded theory about a phenomenon" (Strauss & Corbin, 1990, p.24). This methodology is a general method ofcomparative analysis to realise theory with four central criteria - work, relevance, fit, and modifiability (Creswell, 2002). It will answer the question of 'What was going on in an area?' by generating either a substantive or formal theory - theory related to a case and developed inductively from empirical data to reach an abstract level (Star, 1998). The strongest cases for the use of grounded theory arein studies of comparatively unexplored areas (Samik-Ibrahim, 2000). Grounded theory is used to generate a theory rather than use one 'off the shelf' to enlighten a procedure, action, or interaction, a step-by-step, systematic process to stay close to the data (Creswell, 2002).
Although Glaser's and Strauss's collaborative work led to the introduction of grounded theory, their later works showepistemological differences between them (Glaser, 1978, 1992; Strauss, 1987; Strauss & Corbin, 1990). Glaser has a rigorous positive perspective towards qualitative analysis, while Strauss has a pragmatic epistemology into empirical inquiry through grounded theory. Whereas Glaser's standpoint tends to be more traditional positivism with emphasis on supposition of an objective and external...