1. (a)Consider the following definition of an anomaly: An anomaly is an object that is unusually influential in the creation of a data model.(a) Compare this definition to that of the standard model-based definition of an anomaly.

(b) For what sizes of data sets (small, medium, or large) is this definition appropriate?

2. In one approach to anomaly detection, objects are represented as points in a multidimensional space, and the points are grouped into successive shells, where each shell represents a layer around a grouping of points, such as a convex hull. An object is an anomaly if it lies in one of the outer shells.

(a) To which of the definitions of an anomaly in the first part of the video is this definition most closely related?

(b) Name two problems with this definition of an anomaly.

1)

2)

3. Discuss techniques for combining multiple anomaly detection techniques to improve the identification of anomalous objects. Consider both supervised and unsupervised cases.