residual error compared with estimated measurement uncertainty for \(\pm\sigma\) (in red) and \(\pm2\sigma\) (in orange).  Most points are within one or two standard deviations of zero residual error, as expected for a good fit to the data using Malus's law, but the points do not appear randomly distributed. Instead, there is a weak angular dependence suggesting a small uncorrected systematic misalignment of the light source and/or polarizers with respect to the detector.