## Supplement 1. An R package for fitting zero-inflated binomial models to biological survey data.

## File List

## Description

This is an add-on package for the statistical system R, used to fit zero-inflated binomial distributions to biological survey data by maximum-likelihood estimation. It is known to work with all versions of R above 1.5.0. R can be downloaded from the R Project for Statistical Computing . obserr_0.3-1.zip is a "compiled" package ready for installation in R running under Microsoft Windows, while obserr_0.3-1.tar.gz is a "source" package that requires the R source code development tools for installation, but can be installed in R under any operating system.

In both archives, the source code for all functions is in obserr\R\obserror.R, and html formatted documentation for all functions is available in the zip archive under obserr\chm\*.html. Documentation is also present in the tar and gzip'ed archive, but it is in R documentation format, which can be processed into a variety of formats using the R source development tools.

Under R for Windows, install the downloaded package using the Packages|Install package from local zip file... menu item. Once installed, the functions and associated documentation are made available in a session using the Packages|Load package menu command, or by typing library(obserr) at the command prompt. The documentation on the functions can be accessed either through the HTML index from the R for Windows Help menu, or by typing help(obs.error) at the command prompt after loading the package.