Can library users distinguish between minimum, perceived, and desired levels of service quality? Validating LibQUAL +® using multitrait multimethod analysis

• A multitrait multimethod analysis was used to assess the validity of using gap theory to measure library service quality.
• Gaps should not be computed by simply subtracting scores on the three levels.
• Gaps should be computed only after taking item and error correlations into account.

LibQUAL +® is a widely used measure of library service quality. Based on SERVQUAL's gap theory, LibQUAL +® measures items on three levels of service quality: minimum, perceived, and desired levels. Differences between user evaluations of service quality on these levels indicate the types of gaps in service quality. Gap theory has been criticized due to the possible inability of users to distinguish between different levels. However no study has investigated this claim using statistical analysis. A multitrait multimethod (MTMM) framework was used to evaluate the validity of using three levels of measurement to measure customer satisfaction in LibQUAL +®. Measurement errors across levels of measurement are correlated, indicating that simple score differences are inaccurate estimates of gaps. Users are able to distinguish between the three levels of measurement indicating support for validity of using gap theory in measuring library service quality.