Table 2 Feasibility criteria
Criteria | Measurement | Criteria for continuation to a full trial |
|---|---|---|
Recruitment to cohort rates | Number recruited in 2Â years | % recruited/sample size estimation. Minimum acceptable to proceed to a full-scale trial will consider the number of years needed to recruit the required sample size. Numbers recruited in 2Â years will be extrapolated to determine how long a full trial would need to be. The required sample size will be divided by the percentage recruited in 2Â years. Duration of the full trial of more than 4Â years will not be considered feasible. |
Recruitment to treatment rates | Percentage accepting offer | At least 30%. The percentage of participants refusing treatment will be considered to determine acceptable levels of refusal. Too many treatment refusers may lead to a high chance of a type II error and inadequate information to estimate critical parameters for a full trial with reasonable precision. |
Treatment effects (statistical significance) | Standard mean difference (SMD) CGI | Mean = < .3. Since neither intervention has been tested in this form previously, estimation of the effect size cannot consider previous estimates. Since we need to know that therapies show some evidence of being helpful, a SMD of 0.3 in those implementing the therapies will be considered sufficient to proceed to full trial. |
Treatment effects (clinical significance) | CGI T score | 5 percentiles. A T score change of 5 percentiles is considered clinically significant, since the child has moved from one level of severity to another according to Conners (2009) [47]. |
Attrition: cohort | Number of PQs returned at 6Â months | At least 30% |
Attrition: consultations | Number of consultations attended | Adjustment of intervention provision |
Acceptability of TQ and CQ | Number of TQs and CQs completed at baseline and 6Â months; number of email/telephone/ paper responses | Adjustment of measure, collection methods and trial parameters. Questions reworded or removed dependent on discussion with carers and teachers, and optimum means of delivering questionnaires explored |
Adverse events | Clinicians records | No severe adverse events as defined by the Common Terminology Criteria for Adverse Events guidelines |
Appropriate outcome measurement | Number of missing items | Adjustment of measure |
Recruitment of therapists | Number recruited fulfilling criteria | At least two for each therapy |
Statistical analysis | ANCOVA | Meets assumptions |