Fig. 2. The figure shows the Bland-Altman plot of 22,860 data points, reflecting the differences between each paired reading from the left- and right-sided forehead BIS® electrodes. There was zero bias between the devices. This means that there was no overall tendency for the BISxp® attached to electrodes on either side of the forehead to read higher than its counterpart, attached to electrodes on the opposite side. The  dotted lines show the 95% limits of agreement between the BISxp® readings. The  plot shows the difference between each paired BISxp® reading when the average BISxp® reading ranged between 0 and 100.