Figure 1. The relationship between the Rasch-derived person parameter (attitudes towards driving) and IVF MD.

There was a significant relationship between the Rasch-derived person parameter (attitudes towards driving) and IVF MD (Y = −0.07*X −1.47, R² = 0.023, p = 0.0095). A larger Rasch-derived person parameter value represents a more careful driving attitude. The ‘jitter’ function in the statistical programming language R (ver. 2.15.1, The R Foundation for Statistical Computing, Vienna, Austria) was used to aid interpretation of the scatter plot. Abbreviation. Rasch-derived person parameter: Rasch analysis derived driver's attitude based on the questionnaires of whether they avoid driving at night, in rain, in fog, on highways, high-speed driving, lane changing, driving close to the car in front. IVF MD: integrated visual field mean deviation.