Errata for Linear Mixed Models: A Practical Guide using Statistical Software (Third Edition) Brady T. West, Kathy Welch, Andrzej Galecki 1. On page 48, in Equation (2.30), there is a missing transpose symbol for the first X_i inside the second set of parentheses. h/t to Patrick Wen from Westlake University for catching this; this was missed in the second edition as well! Last updated 8/7/22.