How much of a change in a child’s score on a scale should be considered “real” change?

Answer: Changes that are being measured in research designed to compare the effects of different interventions with each other or with no interventions can be tested as follows: Scores for groups of children receiving the different conditions should be statistically analyzed to see whether there are (a) significant changes from pre-intervention to post-intervention, and (b) whether there are significant group differences in changes. Statistical analyses of group data thus provide a basis for determining whether changes are “real” according to statistical criteria for chance vs. nonchance changes.

A rough approximation to statistical criteria can be applied to scale scores for individual children by comparing the changes with the standard error of measurement for each scale, as follows: (a) On the righthand side of Appendix D, locate the column headed SE of Meas; (b) If you are assessing a child who is considered for mental health services, look in the column headed Ref; (c) if you are assessing a child who is not considered for mental health services, look in the column headed Nonref; (d) look down the column until you reach the scale on which you wish to evaluate change; (e) if a child’s score on a scale has changed more than twice the amount indicated in the appropriate column for the relevant scale, the change exceeds the change that is likely to occur by chance. It should be remembered, however, that the standard error of measurement provides only a rough guideline for judging whether changes in an individual’s scale scores are likely to exceed chance expectations.