The study of software architectures is gaining importance due to its role in various aspects of software engineering such as product line engineering, component based software engineering and other emerging paradigms. With the increasing emphasis on design patterns, the traditional practice of ad-hoc software construction is slowly shifting towards pattern-oriented development. Various architectural attributes like error propagation, change propagation, and requirements propagation, provide a wealth of information about software architectures. In this paper, we show that change propagation probability (CP) is helpful and effective in assessing the design quality of software architectures. We study two different architectures (one that employs patterns versus one that does not) for the same application. We also analyze and compare change propagation metric with respect to other coupling-based metrics.