The analysis of change: Innovations in the visual analysis of data

Methodological reform in psychology calls for research to be more idiographic and less dependent on group statistical inference. Recommended alternatives include more extensive use of graphs and visual analysis. This paper describes the construction and interpretation of modified Brinley plots, a technique for analysing treatment outcomes for individuals within groups that is particularly suitable for outcome research of psychological therapies. Modified Brinley plots are scatter-plots that compare individual scores at time 1 (normally pre-treatment) with scores at various times post-treatment. If the origin and axis scales 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). 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. This talk may be particularly helpful to students planning research into within-participant change over time