1. School of Mathematics, Statistics and Actuarial Science; University of Kent; Canterbury CT2 7FS UK
2. Department of Psychology and Neuroscience; University of Colorado at Boulder; Boulder, Colorado 80309 U.S.A.
3. Department of Psychology; Northeastern University; Boston, Massachusetts 02115 U.S.A.
4. Biostatistics Department; University of Michigan; Ann Arbor, Michigan 48109 U.S.A.
5. Department of Statistics; University of Warwick; Coventry CV4 7AL UK