Researchers are investigating the night time legibility of a highway sign design. They have 30 individuals view a sign at night and, for each individual, the researchers record the maximum distance, in feet, at which the sign can be read. They also record the participants' ages and visual acuities.
Acuity is a eye test measure of visual sharpness.
A high visual acuity means poor clarity of vision. There are two reasons for understanding the relationship between distance and the other two variables. First, the results will be compared to another experiment in which individuals had different ages and acuities. Second, the Federal Highway Administration would like to set sign standards for the general population. There are data available on the age composition of the general population.