The event described—a hurricane causing facility damage and staff absence—is an example of a Special Cause of variation. Special causes (also known as assignable causes) are external, unpredictable, and not inherent to the normal functioning of a process. They represent unusual events that have a significant, often disruptive, impact. The hurricane is a distinct, identifiable event outside the system's routine operation, directly causing the schedule slippage. The primary goal when a special cause is identified is to address its immediate impact and prevent its recurrence, if possible.

A. Common Cause: Incorrect. Common causes are the inherent, predictable, and random variations within a process (the "system noise"). A hurricane is a singular, catastrophic event, not a routine fluctuation.

C. Any one of the above: Incorrect. The cause is specifically a special cause due to its external and unpredictable nature; it cannot be classified as a common cause.

D. Both of the above: Incorrect. A specific cause of variation is classified as either common or special; it cannot be both simultaneously.

1. Deming, W. E. (2018). Out of the Crisis. The MIT Press. In Chapter 9, "Common and Special Causes of Variation and a System," Deming distinguishes between faults of the system (common causes) and specific, assignable events (special causes). A natural disaster like a hurricane is a classic example of a special cause. (pp. 309-315).

2. Montgomery, D. C. (2020). Introduction to statistical quality control (9th ed.). John Wiley & Sons. Chapter 4, "Methods and Philosophy of Statistical Process Control," defines special or assignable causes of variation as arising from external sources not inherent in the process. (Section 4.1, p. 166).

3. MIT OpenCourseWare. (2015). 16.842 Fundamentals of Systems Engineering, Lecture 19: Variation, Lean, and Six Sigma. Massachusetts Institute of Technology. Slide 11 defines Special Cause Variation as "Unpredictable, 'freak' events, outside the 'usual' process," which directly describes the hurricane scenario. Available at: https://ocw.mit.edu/courses/16-842-fundamentals-of-systems-engineering-fall-2015/resources/mit16842f15lec19/