Department of Epidemiology and Biostatistics, Faculty of Medicine, McGill University, Montreal, Quebec H3A 1A2, Canada
We thank Dr. Godbold (1) for noticing the typographic errors in the definition of the weighted average on page 367 of our paper (2). Indeed, as is evident from the standardizing factor in the denominators, the weight for the second of the two sibs must also be w/(1 + 2w). Moreover, as he noted, there should be a plus sign between the contributions of sib1 and sib2.
We also thank Dr. Zou (3) for noting the availability of the alternating logistic regression method in version 8 of SAS software. However, we continue to emphasize that this generalized estimating equation technique for dealing with two or more levels of clustering/hierarchy is limited to binary responses. Irrespective of the type of response, methods other than this one are more suitable for such multilevel data.
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