Final answer:
Trixie does not include hair tugging in her data collection on self-injurious behaviors because it is not as significant as head banging, eye gouging, and self-biting, which are more serious and potentially harmful.
Step-by-step explanation:
Trixie's student engages in a high rate of self-injurious behaviors such as head banging, eye gouging, and self-biting. While collecting data on these behaviors, Trixie does not include hair tugging because, compared to the other behaviors, hair tugging is not significant. Significance in this context refers to the seriousness or severity of the behavior, and how much it impacts student's safety and well-being compared to the more severe behaviors that have been documented. Thus, hair tugging is likely seen as a less harmful behavior that does not require immediate intervention or data collection in the context of Trixie's study. However, it is important to note that all self-injurious behaviors can be concerning and might require attention depending on individual circumstances.