Elien Neimeijer

47 which were collected between June 2017 and July 2018. Participation was voluntary. The researcher provided oral and written information to participants concerning data collec- tion, study aims, and objectives. All participants and their legal guardians were informed that the research was strictly confidential and anonymous. Data were only reported on a living group-level. The multidisciplinary treatment team determined whether a par- ticipant was able to give informed consent to participate. The active consent method was used. All participants gave explicit oral and written consent. Approval for this study was obtained from the Ethics Committee of the Faculty of Social Sciences (ECSS) of the Radboud University (ECSW2017-3001-471). Questionnaires were given a code to guarantee anonymity of participants. Names of participants were replaced by a code to ensure privacy. The questionnaires were used by trained (assistant) researchers of Trajectum, spe- cialised in working with individuals with MID-BIF and forensic histories. If necessary, participants were assisted in completing the questionnaire by a (assistant) researcher who read the questions and answering categories out loud and explained the questions to the participant if necessary. Alternative scripted phrases to enable questions to be explained differently were part of the training they received. If used, this would provide an additional way of checking participants’ understanding while preventing researchers from projecting their interpretation of the questions on to participants. Completed ques- tionnaires were returned to the researcher (first author), and scores were entered into SPSS version 24 (IBM, SPSS Statistics) for analyses. Characteristics on participant level (gender, age, total IQ, legal status, treatment duration at the living group and the facility) and group level (security level, care intensity, composition, and size) were extracted from participants’ records and added to the SPSS database. Data on frequency of aggressive incidents and use of coercive measures were obtained from the facilities’ electronic database (see Instruments). Instruments The Group Climate Instrument. Participants were interviewed about their perception of group climate utilizing the revised Group Climate Instrument (GCI) (Neimeijer, Roest, Van der Helm, & Didden, 2019; Van der Helm, Stams, & Van der Laan, 2011). The GCI is a self-report questionnaire containing 29 items using a 5-point Likert-type scale vary- ing from 1 (‘not applicable’) to 5 (‘entirely applicable’). There is preliminary evidence for