Scoring all versions of the VFSs can be done by simply summing the responses to all test items on a scale (See VFS-Peds User Manual for more details). When using summed scores, higher values reflect more frequent problems with listening-related fatigue. While intuitive, and simple to calculate, this score does not provide the most precise estimate of an individual’s listening-related fatigue (Hornsby et al., 2021). Precision is improved by calculating an IRT (item response theory) scale score. IRT scale scores are standardized scores (e.g., similar to z-scores). A score of 0 reflects the mean magnitude of listening-related fatigue of the study sample. Thus, IRT scores of -3 and +3 would suggest the individual had very low or very high ratings of listening-related fatigue, respectively. IRT scoring takes advantage of variations in sensitivity across test items (an item’s information and threshold discrimination) to provide a more precise estimate of an individual’s listening-related fatigue. To calculate IRT scale scores, however, requires the knowledge and use of appropriate statistical software. As such this scoring method may be more appropriate for research purposes.
For those interested, we have developed custom code for this purpose. The code can be used within the R environment for statistical computing. Links to the software code are provided below. The links direct you to an Open Science Framework (OSF) web page where zip files of the code are stored. On the OSF page simply select the desired folder (e.g., "Generate VFS-A-40 IRT Scores") and then click the "Download as zip" button to save the required files. Instructions for how to use the code are contained in the .R files for a given scale or subscale. For example, instructions for how to calculate IRT scores for the VFS-C (Child self-report) can be found in the "CalcIRT_VFS_C.R" file (within the VFS-Peds zip folder).