The concept of precedent, central to Supreme Court decision making, is based on which legal principle?

Afull irb committee meeting is convened and one agenda item is a new research proposal to evaluate how mothers interact with their learning-disabled child. the inclusion criteria require the children to be a minimum of five years of age. the protocol requires the mother of the child to look at the child without any expression and not to talk to the child for three minutes. the committee determined that the mother's required task may upset the child. the irb approved the study with appropriate language in the parental permission form regarding the possibility that children might become upset. after the start of the study, the principal investigator reports to the irb that, as expected, one of the children became upset. the incident was handled according to the protocol and the child is fine. what should the irb do with regard to this report?