1. Jiguo Cao is an Assistant Professor, Department of Statistics and Actuarial Science, Simon Fraser University, Burnaby, BC, Canada V5A1S6 . James O. Ramsay is a Professor Emeritus, Psychology Department, McGill University, Montreal, Quebec, Canada H3A1B1 . This paper has benefitted substantially from the comments of the editor, an associate editor, and three referees. This research was supported by grants from the Natural Science and Engineering Research Council of Canada to both authors.