A repeated-measures study can ask whether treatment groups differ on average and whether they follow different trajectories over time. These are separate statistical questions. A randomized anesthesia study reported both.
Seventy-two women undergoing gynecologic laparoscopic surgery received one of three anesthetic regimens. Researchers recorded regional cerebral oxygen saturation at four stages, including before induction and after head-down positioning. The analysis found a significant group-by-time interaction, while the overall group effect was not statistically significant.
The interaction indicates that the recorded time courses differed. It does not establish that one regimen produced higher oxygenation at every stage or better neurological recovery. The measure was regional near-infrared spectroscopy. Interpretation requires the timepoint, position and accompanying physiological conditions.