Innovation in the analysis of therapeutic change: Combining both idiographic and nomothetic approaches in one visual analysis
For decades there have been calls for clinical research in psychology to be more idiographic and less dependent on group statistical inference, because what applies in aggregate (nomothetic research) does not necessarily apply to any specific individual (idiographic application). Recommended alternatives include more extensive use of graphs and visual analysis of data. This presentation describes the history, construction and interpretation of modified Brinley plots, a technique for analysing treatment outcomes for individuals within groups that is particularly suitable for therapy outcome research, especially during the treatment-development phase when full randomized controlled trials may be premature. Modified Brinley plots are scatter-plots that compare individual scores at time 1 (normally pretreatment) with scores at various times post-treatment. If the origin and axis scales of the graph are the same no or little change is shown by data points clustering on or about the 45o diagonal line. Change over time (improvement or deterioration) is shown by shifts away from the diagonal. Interpretation is aided by the addition of clinical cut-offs, and by the use of the Reliable Change Index (based on measurement error), features which partition the graph space into meaningful zones. In addition to displaying individuals’ data, these graphs may also display group effects such as means, variances, confidence intervals, and effect sizes. Both between-group and within-group data may be presented and analysed this way and large amounts of data can be efficiently presented and clearly understood within one figure.