Cumulative error distribution functions when fitting rotation matrix functions of azimuth and elevation to the individual mueller matrix elements. The distribution is based on the difference between the best-fit rotation matrix and each individual least-squares based Mueller matrix estimate at every measured azimuth and elevation. Each color corresponds to one of the six Mueller matrix estimates computed using our daytime sky method. The 68% confidence interval falls between errors of 0.04 for some elements and 0.10 for other elements.