Notes that presence of heterogeneous regression slopes in an analysis of covariance design is equivalent to presence of interaction in randomized-blocks design. Describes modification of the usual graphical representation of heterogeneous regressions that can aid in interpreting significant regions for regression surfaces. (NB)

Although single-subject research techniques are valuable to counselors, analyzing change by graphs alone is open to major sources of error. Discusses these sources and explores the issues of serial dependency, unreliability of graphs, interjudge disagreement on graphed data, and the use of time-series statistics with relevance to the counselor in…

Data analysis problems, particularly involving the likelihood of obtaining visually ambiguous graphs, pose a barrier to efforts to promote increased use of single-case evaluation by practitioners. Uses findings from an evaluation of a cognitive-behavioral intervention with adolescent sex offenders to illustrate data analysis problems. (JPS)