For the Rasch analysis item fit (infit mean squares ≥ 1.30), dimensionality and item invariance were assessed.
Also in the confirmatory factor analysis, item 9, "lifting a heavy box", did not perform well.
This paper describes the development of the instrument from factor analysis, item reduction and validation.
As these findings seem to be congruent, we chose in this study to use the remaining seven items (FSS-7) for the analysis of item hierarchy similarity.
From the item analysis, items 13 and 14 were found to be the least suitable; both showed the lowest item total correlations and did not reach the Mittenecker and Ebel selection criteria.
Following the analysis, 79 items remained in the item bank.
After the analysis, the item wordings and overall layout of the Internet survey were changed to improve the simplicity, clarity, and reliability of the scale design.
Ethics approval for the analysis of item responses was granted through the Melbourne Graduate School of Education under application number 0608717.
In the analysis, the item responses were collapsed into a binary category (0 = not at all; 1 = experienced symptoms on any day).
The analysis of item-score correlations looked for correlations greater than 0.40 between items and their own dimension.
