Table 4.
Summary of Fit Statistics for Initial and Final Rasch Analyses of the 16-Item RPQ
| RPQ analyses | Item fit residual |
Person fit residual |
Goodness of fit |
PSI | Significant t tests |
||||
|---|---|---|---|---|---|---|---|---|---|
| Value / SD | Value / SD | χ2 (df) | P | % | % Lower bound (unidimensionality) | ||||
| Initial (16) | -0.47 | 1.40 | -0.30 | 0.95 | 111.37 (80) | 0.01 | 0.84 | 9.87 | 0.48 (NO) |
| Super-items (8)a | -0.49 | 0.67 | -0.37 | 1.02 | 63.77 (72) | 0.74 | 0.87 | 3.59 | 0.73 (YES) |
a
Super-items were created based on residual correlations: “headaches-frustrated,” “dizziness-irritability,” “nausea-longer to think,” “noise sensitivity-restlessness,” “sleep disturbance-forgetfulness,” “fatigue-poor concentration,” “depressed-blurred vision,” and “light sensitivity-double vision.”
df, degrees of freedom; PSI, Person Separation Index; RPQ, Rivermead Post-Concussion Symptoms Questionnaire; SD, standard deviation.