Line-segment confidence bands for repeated measures

For the case of repeated measures on Y with mean values linear in a concomitant variable Z in [a, b], a straight-line confidence band over [a, b] is given with width linear in Z. Graphical presentation of such line-segment confidence bands can help emphasize that appropriate inferences are limited to the range of the data. Because the line-segment bands are designed to cover a finite interval, they are usually more efficient than the widely used hyperbolic bands. Conditions for favorable relative efficiency of area bounded are given. This easily computed trapezoidal confidence region is formulated in terms of a growth-curve model.