The following have not been used as approaches to defining abnormal behavior: statistical infrequency, personal distress, medical school consensus, and violation of norms.

The statement you've provided mentions four different approaches out of which three have been used to define abnormal behavior:

1. Statistical Infrequency: This approach suggests that any behavior that is not common, or is statistically rare, in the general population can be considered abnormal. For instance, an extremely high or extremely low IQ is statistically unusual and hence might be considered abnormal.

2. Personal Distress: According to this approach, behaviors or feelings that cause personal suffering, pain or distress can be classed as abnormal. This is often used when the individual perceives their behavior as problematic, which may or may not be apparent to others.

3. Violation of Norms: This view holds that when someone's behavior deviates significantly from societal or cultural norms, it can be termed as abnormal. What constitutes a norm varies widely across different cultures, so this approach heavily depends on the context.

However, the "medical school consensus" is not an established approach for defining abnormal behavior. Medical consensus refers to a general agreement in the medical community around matters of practice and understanding certain disorders. While it can influence the definition of abnormal behavior by contributing to diagnoses and classifications (like those in the DSM or ICD), it's not a standalone method used to define abnormality.