Hello, I am trying to bootstrap the following statistic: 1- x/y using different sample sizes for x and y (x and y are not paired data). Apparently, only one sample size can be handled, and the na.action (na.exclude) does not work with boot. Could anyone help ? thanks a lot Marie-Agn?s Coutellec UMR CNRS - Universit? 6553 ECOBIO Universit? de Rennes 1 Campus de Beaulieu, Batiment 14 263 avenue du General Leclerc, CS 74205 35042 RENNES Cedex - FRANCE Tel: 33-(0)223235036 marie-agnes.coutellec at univ-rennes1.fr http://www.umr6553.univ-rennes1.fr