Refer to the Robotica (Vol. 22, 2004) study of the effectiveness of display devices for three virtual reality (VR)-based hand rehabilitation systems, Exercise 14.10 (p. 756). Display device A is a projector, device B is a desktop computer monitor, and device C is a head-mounted display. Recall that 12 nondisabled, right-handed male subjects were randomly assigned to the three VR display devices, four subjects in each group. Additionally, within each group two subjects were randomly assigned to use an auxiliary lateral image and two subjects were not. Consequently, a factorial design was employed, with VR display device at three levels (A, B, or C) and auxiliary lateral image at two levels (yes or no). Each subject carried out a “pick-andplace” procedure using the assigned VR system, and the collision frequency (number of collisions between moved objects) was measured.

a. Give the sources of variation and associated degrees of freedom in an ANOVA summary table for this design.
b. Write the complete model for analyzing these data. The degrees of freedom for each source, part a, should correspond with the number of dummy variable terms for that source in the model.
c. The factorial ANOVA resulted in the following p-values: display main effect (.045), auxiliary lateral image main effect (.003), and interaction (.411). Interpret, practically, these results. Use for each test you conduct.