The Internal Consistency of the ISO/IEC 15504 Software Process Capability Scale

ISO/IEC 15504 is an emerging international standard for software process assessment. It has recently undergone a major change in the rating scale used to measure the capability of processes. The objective of this paper is to present a follow up evaluation of the internal consistency of this process capability scale. Internal consistency is a form of reliability of a subjective measurement instrument. A previous study evaluated the internal consistency of the first version of the ISO/IEC 15504 document set (also known as SPICE version 1). In the current study we evaluate the internal consistency of the second version (also known as ISO/IEC PDTR 15504). Our results indicate that the internal consistency of the capability dimension did not deteriorate, and that it is still sufficiently high for practical purposes. Furthermore, we identify that the capability scale has two dimensions that we termed “Process Implementation” and “Quantitative Process Management”.