I have just noticed that a couple of ='s should be <-'s in my question. Repeating everything with the corrections made does not resolve my questions.
Dr Murray Jorgensen http://www.stats.waikato.ac.nz/Staff/maj.html Department of Statistics, University of Waikato, Hamilton, New Zealand Email: maj at waikato.ac.nz Fax 7 838 4155 Phone +64 7 838 4773 wk +64 7 849 6486 home Mobile 021 395 862