Orientation clue experiment. Human Factors (Dec. 1988)

published a study of color brightness as a body orientation clue. Ninety college students reclining on their backs in the dark were disoriented when positioned on a rotating platform under a slowly rotating disk that blocked their field of vision. The subjects were asked to say “Stop” when they felt as if they were right-side up. The position of the brightness pattern on the disk in relation to each student’s body orientation was then recorded. Subjects selected only three disk brightness patterns as subjective vertical clues: (1)

brighter side up, (2) darker side up, and (3) brighter and darker sides aligned on either side of the subjects’ heads.

The frequency counts for the experiment are given in the accompanying table. Conduct a test to compare the proportions of subjects who fall into the three disk-orientation categories. Assume that you want to determine whether the three proportions differ. Use a = .05.

Disk Orientation Brighter Side Up Darker Side Up Bright and Dark Sides Aligned 58 15 17