The Staffing and Resource Adequacy sub scale was highly correlated with the direct staffing measure used in our analyses
(ρ = –0.42; p < 0.001) and was thus excluded from calculation of the composite PES-NWI score.
We aggregated the remaining four PES sub scale means for critical care nurses to the hospital level to generate a composite nurse work environment score, as previously done (23, 24, 29, 30).