This paper summarizes the complete range of analog defects and resultant faults. A complete set of metrics is then derived for measuring the quality of analog tests. The probability-based equations for fault coverage, defect level, yield coverage, and yield loss are self-consistent, and consistent with existing equations for digital test metrics. We introduce the concept of partial coverage, show that it is inherent to analog testing, and show that coverage cannot be calculated without knowing the performance specifications for a circuit, as well as the process parameter distributions. Practical methods for calculating probabilities are discussed, and simple, illustrative examples given.