The type of rating method used (dichotomous, ordinal or interval) determines the type of mathematical analysis to be carried out as well as the the length and duration of the test administration. As before, the criteria for selection depend on the researcher's objectives and on the capacities of the person to be assessed. If an intellectual or perceptual deficit exists, then a simpler problem-focused procedure is recommended. The advantages of each type of rating system are discussed in the next chapter, since they are very closely related to how the grid must be applied.
It is important to plan how many grids are to be administered and when. If the investigator is interested in evaluating the change resulting from therapy, the grid must be administered at least once at the start of treatment and again upon its completion. An additional administration at follow-up is also advisable. In other cases, more administrations of the grid may be necessary depending on the objectives of the investigator, e.g., if one wishes to study the process of conceptual change over the course of therapy.
A working knowledge of the overall grid procedure as well as a clear idea of the information to be gathered is necessary if a grid is to be designed accurately. In general, a design that extracts the most relevant information in the shortest timespan is recommended. The time factor in the administration of the grid can be crucial in large-scale studies as well as in clinical work. Administration of the grid asks that the interviewee reply to a considerable number of questions, thus requiring the investigator to consider the influence of respondent fatigue when interpreting the results. Although the average time taken to administer the grid varies from 45 to 60 minutes, there are various factors that can influence the time needed for completion, regardless of the respondent's own pace. The decision to provide or to elicit constructs and the final number of elements used can all influence the time taken to complete the grid. With reference to the latter, Rivas and Marcos (1985) carried out a bibliographical study based on a large number of published studies that used the repertory grid technique. They found that the average number of elements ranges from ten to fifteen and that the typical number of constructs is usually slightly less than the number of elements. For the results of a grid design to be valid, we suggest using a minimum of ten elements and constructs.
(Names and certain information have been changed to protect the client's identity. Feixas (1991) has already made a first presentation of this case).
Daniel was referred to a private outpatient psychotherapy clinic by a trainee therapist of the same centre. Upon intake, Daniel, a 27-year old teacher, married and with one child, had suffered a series of recurrent panic attacks for a period of three months. His symptoms fit the DSM-III-R criteria for the diagnosis of panic attacks (without agoraphobia) of moderate severity. During the first session, the client showed evident signs of anxiety related to the anticipation of another panic attack in addition to fear of going mad. He found it extremely difficult to keep up with normal, everyday activities (he was unable to drive) and was, at the start of treatment, on sick leave. With the aid of psychotherapeutic treatment, the client recovered a normal level of functioning, returned to work, and his anxiety levels decreased considerably after three months. The therapeutic approach applied to this case can be defined as cognitive-constructivist (Feixas & Villegas, 1993; Kelly, 1955; Mahoney, 1991). However, it is worth emphasizing that the repertory grid is not limited to studying this approach to therapy and can be appropriate for assessing conceptual change resulting from any kind of therapeutic intervention.
The repertory grid was administered almost immediately after the initial intake interview and data-gathering session. As noted before, the design of the grid depends on the objectives of the study and on what the investigator wishes to assess. In this example, we wanted to study the client's construct system with reference to his interpersonal relations, so the design of the personal others grid was applied to this case. Personal elements such as "self" and "meaningful others" from his family were included, accordingly. We decided to elicit rather than provide personal constructs, since our initial intention was to become familiar with Daniel's personal meanings. The rating system selected was a 7-point rating scale (see next chapter), as the client had no learning or comprehension deficit. In order to facilitate a mathematical comparison of the results, we decided to administer a grid every three months following the initial administration using the same elements and constructs elicited in the first session. For the sake of brevity, only the first and last repertory grids are compared in this manual in Chapter VI to illustrate how clinical change can be evaluated.