Measuring Agile Agreement: Development and Validation of the Manifesto and Principle Scales

While the importance of human factors in agile software development is widely acknowledged, the measurement of an individual's "agile agreement" remains an ill-defined and challenging area. A key limitation in existing research is the failure to distinguish between agreement with the abstract, high-level values of the Agile Manifesto and agreement with the concrete, day-to-day practices derived from the 12 Principles. This paper addresses this methodological gap by presenting the design and validation of two distinct instruments: the novel Manifesto Agreement Scale (MAS), and the Principle Agreement Scale (PAS), which is a systematic adaptation and refinement of a prior instrument. We detail the systematic process of item creation and selection, survey design, and validation. The results demonstrate that both scales possess important internal consistency and construct validity. A convergence and divergence analysis, including Proportional Odds Logistic Regression, a Bland-Altman plot, and an Intraclass Correlation Coefficient (ICC), reveals that while the two scales are moderately correlated, they are not interchangeable and capture distinct dimensions of agile agreement. The primary contribution of this work is a pair of publicly available instruments, validated within a specific demographic of Belgian IT professionals. These scales represent a critical initial step toward facilitating a more nuanced measurement of agile agreement, distinguishing agile agreement across various levels of perception and aiding in a more refined interpretation of person-agile fit.