Classical Test Theory and Item Response Theory Analyses of Multi-Item Scales Assessing Parents' Perceptions of Their Children's Dental Care

BACKGROUND: Classical test theory and item response theory methods can provide useful and potentially different insights into the performance of items in a survey designed to elicit parental perceptions of dental care delivered to children in publicly funded programs. OBJECTIVES: The authors sought to illustrate the use of both classical test theory and item response theory to evaluate survey instruments. METHODS: Using 2 years of cross-sectional data collected from enrollees in dental plans in 2001 and 2002, the authors studied families with children between ages 4 to 18 who were enrolled in 1 of 5 dental plans for 12 months or longer. The 2001 survey yielded a total of 2536 usable surveys and the 2002 survey yielded 2232 useable surveys (50% and 46% response rate, respectively) for a total sample size of 4036 children who used the plan for most or all of their care. MEASURES: The beta version of the CAHPS(R) dental care survey instrument includes 2 global rating items (dental care, dental plan) and multi-item scales assessing getting needed care, getting care quickly, communication with dental providers, office staff, and customer service. RESULTS: Item missing data rates were low. Item-scale correlations for hypothesized scales (corrected for overlap) tended to exceed correlations of items with other scales. Classical test theory analyses identified 5 of 10 communication items that did not perform well. Internal consistency reliability estimates for the scales ranged from 0.73 to 0.86. Item response theory painted a more promising picture than classical test theory for the 2 communication items that assessed access to an interpreter when needed. CONCLUSIONS: The beta CAHPS(R) dental survey performed well and the revised instrument is recommended for future studies. Classical test theory and item response theory can provide complementary information about survey items.