Only DYFS referrals to family preservation in the selected sites were considered for random assignment. Excluded from the study were cases referred by non-DYFS sources, cases served in family preservation prior to the study that were returning for a second "booster" service, and reunification cases.
DYFS uses a broad definition of reunification as a referral criterion. The policy does not put time limits on how long a child was in placement. Caseworker, supervisor, and screener jointly decide whether a child is considered being reunified from a placement or whether the case is considered a placement prevention case, that is, the goal was preventing the child from entering a long-term placement. For the study we used a guideline of seven days. If a child had been in placement more than 7 days, we excluded him or her from the study. Although this process was monitored closely, nine such cases entered the study, but were removed from the analyses because children were in care for longer than seven days at the time of random assignment.
DYFS workers could also re-refer a case for FPS anytime after the completion of the program. This "booster" or "booster shot" still must meet the criteria of "imminent risk" and has a maximum service of four weeks. There is no maximum waiting time between the first period of intervention and the booster; however, after a year, a booster would be counted as a full case with a new case number. Cases being referred for booster service where the original FPS service was conducted prior to the study were excluded from random assignment.