The ICH E14 guidance recommends the use of time-matched baseline while others recommend alternative baseline definitions including day-averaged baseline. In this paper, we consider six models adjusting for baselines. We derive the explicit covariances and compare their power under various conditions. Simulation results are provided. We conclude that type I error rates are controlled. However, one model outperforms the others on statistical power under certain conditions. In general, the ANCOVA model using day-averaged baseline is preferred. If the time-matched baseline has to be used as per requests from regulatory agencies, the by time-point analysis using ANCOVA model should be recommended.