They reported DDP to be an effective treatment for children with complex trauma who met the DSM IV criteria for reactive attachment disorder. The first report concluded that children who received dyadic developmental psychotherapy had clinically and statistically significant improvements in their functioning as measured by the Child Behavior Checklist, while the children in the control group showed no change one year after treatment ended. The study also used the Randolph Attachment Disorder Questionnaire as a measure, which has not been empirically validated for reactive attachment disorder. Statistical comparisons were performed using multiple t-tests rather than an analysis of variance; this has been criticized because t-tests increase the chance of finding any significant differences. The treatment group comprised thirty-four subjects whose cases were closed in 2000/01. This was compared to a "usual care group" of thirty subjects, who were treated elsewhere. The published reports on this work do not specify the nature of "usual care" or clarify why the "usual care" group, who were assessed at Becker-Weidman's clinic, did not have treatment there. Treatment consisted of an average of 23 sessions over eleven months. The findings continued for an average of 1.1 years after treatment ended for children between the ages of six and fifteen years. There were no changes in the usual care-group subjects, who were re-tested an average of 1.3 years after the evaluation was completed. In the follow-up study the results from the original study were maintained an average of 3.9 years after treatment ended. There were no changes in the usual care-group subjects, who were re-tested an average of 3.3 years after the evaluation was completed. Becker-Weidman's first study was considered by the APSAC Taskforce in their November 2006 Reply to Letters following their main report on attachment therapy. The Taskforce had in their original report criticised Becker-Weidman for claiming an evidence base to his therapy, and indeed for claiming to be the only evidence based therapy, where the Taskforce considered no evidence base existed. Becker-Weidman responded to this with an open letter citing his study. The Taskforce examined the (2006) study, criticized the methodology and stated that although the study was an important first step towards learning the facts about DDP outcomes, it fell far short of the criteria that must be met before designating a treatment as evidence based. Between the Taskforce report and Reply to Letters, Craven & Lee (2006) undertook a literature review of 18 studies of interventions used for foster children and classified them under the controversial Saunders, Berliner, & Hanson (2004) system.