Using item response theory to develop a shortened practice environment scale of the nursing work index.

The 31-item Practice Environment Scale of the Nursing Work Index (PES-NWI) has been frequently used globally to measure the nurse work environment. However, due to its length and subsequent respondent burden, a more parsimonious version of the PES-NWI may be desirable. Item response theory (IRT) is a statistical technique that assists in decreasing the number of items in an instrument without sacrificing reliability and validity. Two separate samples of nurses in the United States (one called the "internal data source" and the other called "external data source"; sample sizes = 843 and 722, respectively) were analyzed. The internal data source was randomly split into training (n = 531) and validating data sets (n = 312), while a separate whole external data source was used as the final validating data set. Using IRT with training data, we removed nine items; two additional items were removed based on recommendations from a previous study. Confirmatory factor analyses supported the validity of the measurement model with the 20-item of PES-NWI in both internal and external validation data sources. The correlations among subscales between 31- and 20-item versions were high magnitude for five subscales in both validation data sets (τ = 0.84-0.89). Ultimately, we identified a 20-item version of the PES-NWI which demonstrated adequate validity and reliability properties while decreasing data collection burden yet maintaining a similar factor structure to the original instrument. Additional research may be necessary to update the items themselves on the PES-NWI.