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The measurement framework provides the necessary requirements and rules for the capability dimension. It defines a schema which enables an assessor to determine the capability level of a given process. These capability levels are defined as part of the measurement framework.
To enable the rating, the measurement framework provides process attributes defining a measurable property of process capability. Each process attribute is assigned to a specific capability level. The extent of achievement of a certain process attribute is represented by means of a rating based on a defined rating scale. The rules from which an assessor can derive a final capability level for a given process are represented by a process capability level model.
Automotive SPICE 3.1 uses the measurement framework defined in ISO/IEC 33020:2015.
NOTE: Text incorporated from ISO/IEC 33020 within this chapter is written in italic font and marked with a left side bar.
3.2.1. Process capability levels and process attributes
Process attributes are features of a process that can be evaluated on a scale of achievement, providing a measure of the capability of the process. They are applicable to all processes.
A capability level is a set of process attribute(s) that work together to provide a major enhancement in the capability to perform a process. Each attribute addresses a specific aspect of the capability level. The levels constitute a rational way of progressing through improvement of the capability of any process.
According to ISO/IEC 33020 there are six capability levels, incorporating nine process attributes:
Level 0: Incomplete process | The process is not implemented, or fails to achieve its process purpose. |
Level 1: Performed process | The implemented process achieves its process purpose |
Level 2: Managed process | The previously described performed process is now implemented in a managed fashion (planned, monitored and adjusted) and its work products are appropriately established, controlled and maintained. |
Level 3: Established process | The previously described managed process is now implemented using a defined process that is capable of achieving its process outcomes. |
Level 4: Predictable process | The previously described established process now operates predictively within defined limits to achieve its process outcomes. Quantitative management needs are identified, measurement data are collected and analyzed to identify assignable causes of variation. Corrective action is taken to address assignable causes of variation. |
Level 5: Innovating process | The previously described predictable process is now continually improved to respond to organizational change. |
Table 10 — Process capability levels according to ISO/IEC 33020
Within this process assessment model, the determination of capability is based upon the nine process attributes (PA) defined in ISO/IEC 33020 and listed in Table 11.
Attribute ID | Process Attributes |
Level 0: Incomplete process | |
Level 1: Performed process | |
PA 1.1 | Process performance process attribute |
Level 2: Managed process | |
PA 2.1 | Performance management process attribute |
PA 2.2 | Work product management process attribute |
Level 3: Established process | |
PA 3.1 | Process definition process attribute |
PA 3.2 | Process deployment process attribute |
Level 4: Predictable process | |
PA 4.1 | Quantitative analysis process attribute |
PA 4.2 | Quantitative control process attribute |
Level 5: Innovating process | |
PA 5.1 | Process innovation process attribute |
PA 5.2 | Process innovation implementation process attribute |
Table 11 — Process attributes according to ISO/IEC 33020
3.2.2. Process attribute rating
To support the rating of process attributes, the ISO/IEC 33020 measurement framework provides a defined rating scale with an option for refinement, different rating methods and different aggregation methods depending on the class of the assessment (e.g. required for organizational maturity assessments).
Rating scale
Within this process measurement framework, a process attribute is a measureable property of process capability. A process attribute rating is a judgement of the degree of achievement of the process attribute for the assessed process.
The rating scale is defined by ISO/IEC 33020 as shown in table 12.
N | Not achieved | There is little or no evidence of achievement of the defined process attribute in the assessed process. |
P | Partially achieved | There is some evidence of an approach to, and some achievement of, the defined process attribute in the assessed process. Some aspects of achievement of the process attribute may be unpredictable. |
L | Largely achieved | There is evidence of a systematic approach to, and significant achievement of, the defined process attribute in the assessed process. Some weaknesses related to this process attribute may exist in the assessed process. |
F | Fully achieved | There is evidence of a complete and systematic approach to, and full achievement of, the defined process attribute in the assessed process. No significant weaknesses related to this process attribute exist in the assessed process. |
Table 12 — Rating scale according to ISO/IEC 33020
The ordinal scale defined above shall be understood in terms of percentage achievement of a process attribute.
The corresponding percentages shall be:
N | Not achieved | 0 to ≤ 15% achievement |
P | Partially achieved | > 15% to ≤ 50% achievement |
L | Largely achieved | > 50% to ≤ 85% achievement |
F | Fully achieved | > 85% to ≤ 100% achievement |
Table 13 — Rating scale percentage values according to ISO/IEC 33020
The ordinal scale may be further refined for the measures P and L as defined below.
P- | Partially achieved: | There is some evidence of an approach to, and some achievement of, the defined process attribute in the assessed process. Many aspects of achievement of the process attribute may be unpredictable. |
P+ | Partially achieved: | There is some evidence of an approach to, and some achievement of, the defined process attribute in the assessed process. Some aspects of achievement of the process attribute may be unpredictable. |
L- | Largely achieved: | There is evidence of a systematic approach to, and significant achievement of, the defined process attribute in the assessed process. Many weaknesses related to this process attribute may exist in the assessed process. |
L+ | Largely achieved: | There is evidence of a systematic approach to, and significant achievement of, the defined process attribute in the assessed process. Some weaknesses related to this process attribute may exist in the assessed process. |
Table 14 — Refinement of rating scale according to ISO/IEC 33020
The corresponding percentages shall be:
P- | Partially achieved - | > 15% to ≤ 32.5% achievement |
P+ | Partially achieved + | > 32.5 to ≤ 50% achievement |
L- | Largely achieved - | > 50% to ≤ 67.5% achievement |
L+ | Largely achieved + | > 67.5% to ≤ 85% achievement |
Table 15 — Refined rating scale percentage values according to ISO/IEC 33020
Rating and aggregation method
ISO/IEC 33020 provides the following definitions:
A process outcome is the observable result of successful achievement of the process purpose.
A process attribute outcome is the observable result of achievement of a specified process attribute.
Process outcomes and process attribute outcomes may be characterised as an intermediate step to providing a process attribute rating.
When performing rating, the rating method employed shall be specified relevant to the class of assessment. The following rating methods are defined.
The use of rating method may vary according to the class, scope and context of an assessment. The lead assessor shall decide which (if any) rating method to use. The selected rating method(s) shall be specified in the assessment input and referenced in the assessment report.
ISO/IEC 33020 provides the following 3 rating methods:
