Under a defect classification system, a nonconformance that could cause a product's usability to be substantially reduced would be classified as

A major defect is defined as a nonconformance, other than critical, that is likely to result in failure or to materially reduce the usability of the product for its intended purpose. The phrase "substantially reduced" usability in the question directly corresponds to the definition of a major defect. This classification distinguishes it from a minor defect, which has little impact on usability, and a critical defect, which typically involves safety hazards or complete functional failure. Therefore, a nonconformance that substantially reduces a product's usability is classified as major.

A. acceptable: A nonconformance is a failure to meet a requirement and is, by definition, not acceptable without disposition.
B. minor: A minor defect is a nonconformance that is not likely to materially reduce the usability of the product for its intended purpose.
D. critical: A critical defect is one that could result in hazardous or unsafe conditions for individuals or cause a complete failure of the product's primary function.

1. ASQ Quality Press. (2017). The Certified Quality Engineer Handbook (4th ed.). In Chapter 21

"Acceptance Sampling

" the text defines a major defect as "one that is likely to result in failure or to materially reduce the usability of the product for its intended purpose" (p. 298).

2. ANSI/ASQ Z1.4-2008 (R2018). Sampling Procedures and Tables for Inspection by Attributes. American Society for Quality. Section 4.4

"Classification of defects

" defines a Major Defect as "A defect

other than critical

that is likely to result in failure

or to reduce materially the usability of the unit of product for its intended purpose."

3. Gryna

F. M.

Chua

R. C. H.

& DeFeo

J. A. (2017). Juran's Quality Planning and Analysis: From Product Development Through Use (6th ed.). McGraw-Hill Education. Chapter 13

"Inspection

Test

and Measurement

" discusses the classification of defects

aligning with the standard definitions where a major defect materially reduces usability.