[Study of development of public health safety literacy scale in China]

Objective: To develop a suitable scale for assessing the public health safety literacy in residents in China. Methods: The initial scale of Chinese public health safety literacy was developed through theoretical conceptualization, item pooling, field verifying and item inclusion and exclusion. Then the initial scale was converted into an electronic questionnaire. A total of 2 809 residents from 4 provinces were randomly selected for field testing. Classical test theory (CTT) and item response theory (IRT) were used for item reduction. SPSS 23.0 was used for exploratory factor analysis (EFA) and unidimensional testing. Package R 4.1.1 ltm and mirt were used for the analysis of the psychometric properties of items and generate the ICC, IIC and TIF. Results: The initial scale had 30 items (B1-B30), and the test took 9.8 s to complete one item averagely. According to the CTT, B2 was deleted due to coefficient of total correlation (CITC) <0.3 and the item-dimension correlation coefficient (IDCC) <0.4. B23 was deleted due to CITC<0.3, IDCC<0.4 and difficulty index (W) <0.2. B30 was deleted due to CITC<0.3 and W<0.2. The total Cronbach's α of the scale was 0.923 after deletion. EFA indicated that 14 items should be deleted due to lower factor loadings <0.7. EFA was conducted for remaining 13 items and 2 common factors were extracted, the factor loadings of all items were >0.7, the accumulated variance contribution of the 2 common factors was 63.361%, and the total Cronbach's α was 0.891, showing unidimensionality, IRT was used to test the remaining items. B14 and B20 were deleted due to discrimination coefficient (a) <0.3, difficulty threshold coefficient (b) ∉[-3,3], the small amount of information and the flat, crowded, non-monotonic ICC, and IIC. Finally, the Cronbach's α of the 11-itemed scale was 0.936 with TLI=0.97, CFI=0.99, and RMSEA=0.03. Conclusion: The final scale has good reliability, validity, discrimination, difficulty level and feasibility, and can be applied for the rapid assessment of public health safety literacy in China.