1. 1.

   If you import data that are decimal comma separated with the default settings (i.e., with decimal point separation) or vice versa, R will see all variables as factors, and thestrcommand will tell you so. Hence, to check that data were imported correctly, we recommend always using thestr command on the imported data frame immediately after importing the data.

2. 2.

   A mixed effects model is an extension of linear regression.

3. 3.

   A sex/year interaction term allows the effect of sex to differ over the years.

Authors and Affiliations

1. Highland Statistics Ltd., 6 Laverock Road, Newburgh, UK, AB41 6FN

   Alain F. Zuur & Elena N. Ieno

2. IMARES, Institute for Marine Resources & Ecosystem Studies, 1797 SH ’t Horntje, The Netherlands

   Erik H. W. G. Meesters

Corresponding author

Correspondence toAlain F. Zuur.

Reprints and permissions

© 2009 Springer Science+Business Media, LLC

Policies and ethics