Validation of the Workplace Integrated Safety and Health (WISH) assessment in a sample of nursing homes using Item Response Theory (IRT) methods

OBJECTIVES: To validate and test the dimensionality of six constructs from the Workplace Integrated Safety and Health (WISH) assessment, an instrument that assesses the extent to which organisations implement integrated systems approaches for protecting and promoting worker health, safety and well-being, in a sample of nursing homes in the USA. DESIGN: Validation of an assessment scale using data from a cross-sectional survey. SETTING: Nursing homes certified by the Centers for Medicaid and Medicare services in three states of the USA: Ohio, California and Massachusetts. PARTICIPANTS: 569 directors of nursing from nursing homes serving adults and with more than 30 beds participated in the study. RESULTS: Graded response Item Response Theory (IRT) models showed that five out of six constructs were unidimensional based on balanced interpretation of model fit statistics—M2 or C2 with p value >0.05, Comparative Fit Index >0.95, lower bound of the root mean squared error of approximation 90% CI <0.06 and standardised root mean square residual <0.08. Overall measure and construct reliability ranged from acceptable to good. Category boundary location parameters indicated that items were most informative for respondents in lower range of latent scores (ie, β(1), β(2), β(3) typically below 0). A few items were recommended to be dropped from future administrations of the instrument based on empirical and substantive interpretation. CONCLUSIONS: The WISH instrument has utility to understand to what extent organisations integrate protection and promotion of worker health, safety and well-being; however, it is most informative in organisations that present lower scores.