Within an ISO process assessment, a capability level is said to be established 'only' and 'only if' all the process attributes are 'fully achieved'.

ISO/IEC process-assessment standards (ISO/IEC 15504 and its successor ISO/IEC 33020) state that a capability level n is achieved when:
1. Every process attribute (PA) at level n is rated at least “Largely achieved” (≥ 50 %); and
2. Every PA of all lower capability levels (1…n-1) is rated “Fully achieved” (≥ 85 %). Thus, the standard does not require all PAs at the target level to be “Fully achieved”; “Largely achieved” is sufficient. Therefore the assertion that a capability level is established only when all PAs are fully achieved is incorrect. Why the other option is wrong:
• True – Incorrect because it ignores the ISO rule that allows a “Largely achieved” rating for the PAs of the level being claimed; only lower-level PAs must be “Fully achieved.”

1. ISO/IEC 15504-2:2003, Clause 4.5.4 “Determination of process capability level”, pp. 18-19.

2. ISO/IEC 33020:2015, Clause 7.3.2 “Criteria for capability level rating”, p. 16.

3. García, F. et al., “An Overview of ISO/IEC 15504 (SPICE)”, Software Quality Journal, 2004, Section 3.2, DOI: 10.1023/B:SQJO.0000013324.00459.a7.

4. University of Oulu, Course “Software Process Improvement”, Lecture 6, slide 19 (2021).