Non-Gaussian Error Distributions of LMC Distance Moduli Measurements

Abstract

We construct error distributions for a compilation of 232 Large Magellanic Cloud (LMC) distance moduli values from de Grijs (2014) that give an LMC distance modulus of (m-M)_{0}=18.49 plus/minus 0.13 mag (median and 1 sigma symmetrized error). Central estimates found from weighted mean and median statistics are used to construct the error distributions. The weighted mean error distribution is non-Gaussian --- flatter and broader than Gaussian --- with more (less) probability in the tails (center) than is predicted by a Gaussian distribution; this could be the consequence of unaccounted-for systematic uncertainties. The median statistics error distribution, which does not make use of the individual measurement errors, is also non-Gaussian --- more peaked than Gaussian --- with less (more) probability in the tails (center) than is predicted by a Gaussian distribution; this could be the consequence of publication bias and/or the non-independence of the measurements. We also construct the error distributions of 247 SMC distance moduli values from de Grijs (2015). We find a central estimate of (m-M)_{0}=18.94 plus/minus 0.14 mag (median and 1 sigma symmetrized error), and similar probabilities for the error distributions.