Substantial Majority (per ASHRAE) is defined as

• A. 50% or more
• B. 80% or more
• C. 90% or more
• D. 100%

Answer: (B)

Substantial majority signals a strong level of agreement or prevalence used in ASHRAE guidance. It is defined as eighty percent or more. This threshold is chosen to indicate broad consensus without demanding perfection, which is rarely achievable in real-world data. A simple majority (over fifty percent) is too low to imply strong support, while requiring ninety percent or more or unanimity (100%) would be overly strict for practical decisions. So, eighty percent or more best captures a robust level of agreement. For example, if 80 out of 100 respondents favor a proposed ventilation approach, that meets this criterion.