# Engineering the Future: Evaluation of Virtual Reality Across Project Lifecycle Stages
## 4 Results
### Confirmatory Factor Analysis of Perceived Practiality of VR Across Project Lifecycle Stages
While an iterative analysis to determine McDonald's Omega Total if each item was deleted was part of the analysis procedure, an error encountered during its execution prevented these specific values from being reported. Additionally, McDonald's Omega was calculated from a unidimensional Confirmatory Factor Analysis (CFA) model. This model was fit using an estimator appropriate for ordinal data. This model-based Omega for the eight-item scale was 0.76 (more precisely, 0.759). An attempt to calculate this model-based Omega iteratively, if each item were deleted, resulted in NA values for all items. This suggests that the sub-models, each with seven items, may have encountered convergence issues or other problems during the estimation or the subsequent reliability calculation. In summary, the scale measuring the perceived practicality of VR demonstrates acceptable internal consistency, as indicated by an Ordinal Alpha of 0.75 and McDonald's Omega Total values around 0.76. The item-total statistics for Ordinal Alpha clearly identify the item Specification and Requirement Definition as problematic for the scale's reliability. Its very low corrected item-total correlation (0.13) and the observation that its removal increases the Ordinal Alpha to 0.78 strongly suggest that this item either measures a different aspect or introduces statistical noise. This conclusion is further corroborated by its near-zero loading on the general factor in the McDonald's Omega analysis. Items such as Design and Surveys and Development appear to be the strongest contributors to the scale's reliability. This is evidenced by their high corrected item-total correlations and the substantial drop in Ordinal Alpha that would occur if they were removed, as well as their high factor loadings in the omega analysis. The other items contribute adequately to the overall consistency of the scale. The initial model fit was suboptimal (\(\chi^{2}=40.02\), df = 20, \(p=0.005\); CFI = 0.94; TLI = 0.92; RMSEA = 0.14 (90% CI [0.07, 0.20]); SRMR = 0.12). The indicator for Specification and Requirement Definition had a nonsignificant loading (b = 0.40, SE = 0.32, z = 1.24, \(p=0.21\); \(\beta=0.17\)) and was excluded from the final model. Model refinement was guided by Modification Indices, leading to the addition of five residual covariances between related stages. These included, for example, covariances between Proposal and Investor Recruitment and Testing (Cov = \(-\)0.29, \(p<0.001\)) and between Maintenance and Training (Cov = 0.26, \(p<0.01\)), capturing shared variance due to conceptual proximity. The revised model (Figure 2) demonstrated excellent fit: \(\chi^{2}(9)\) = 4.49, \(p=0.88\); CFI = 0.98; TLI = 0.97; RMSEA = 0.00 (90% CI [0.00, 0.08]); SRMR = 0.05. All remaining indicators had statistically significant loadings on the latent variable perceived practicality of VR. The unstandardized factor loadings (b) ranged from 0.95 to 1.98, with standard errors (SE) ranging from 0.35 to 0.69. Corresponding z-values ranged from 2.62 to 3.17, and \(p\)-values ranged from 0.009 to 0.002. The standardized loadings (\(\beta\)) ranged from 0.39 to 0.82, confirming that each indicator meaningfully contributed to the unidimensional structure of perceived VR practicality. The final set of retained stages included Proposal and Investor Recruitment, Concept Formation, Design and Surveys, Development, Testing, Training, and Maintenance. Among them, Design and Surveys, Development, and Testing showed the strongest contributions to the latent construct. This refined model confirms the unifactorial structure of perceived practicality and identifies the project stages where VR is seen as most useful, providing a solid basis for further structural analysis.