On page 11 of our publication , the correction for missing data in a discrete Γ distribution was conducted as
This correction, equation (1), is only correct when the category probabilities pjhave no effect on observability. Because the category probabilities have an effect on observability, the appropriate correction is
Here N is the total number of gene families and M is the number of rate categories. Analyses based on equation (2) as opposed to equation (1) revealed remarkably similar results and all conclusions made based on the old method remain qualitatively unchanged. The additional analyses and the altered tables are provided in Additional File 1 and also available at http://evol.mcmaster.ca/~weilong/research.html. We thank Dr. Matt Spencer for pointing out the difference in averaging methods and thank Drs. David Bryant, Ofir Cohen, Miklós Csűrös, Tal Pupko, and Ed Susko for communication of ideas.
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