Letter to the editor
Date of Issue2013
School of Physical and Mathematical Sciences
No abstract available.
The annals of applied statistics
© 2013 Institute of Mathematical Statistics. This paper was published in The Annals of Applied Statistics and is made available as an electronic reprint (preprint) with permission of Institute of Mathematical Statistics. The paper can be found at the following official DOI: [tp://dx.doi.org/10.1214/13-AOAS640]. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper is prohibited and is subject to penalties under law.