Are instructor reviews through ETS really anonymous?

I have been requested by my college to fill out an instructor evaluation administered through ETS.org (Educational Testing Service). The ETS e-mail states “All responses from the survey are completely confidential; any information that could identify you will not be associated with your survey responses.” However, I want to make absolutely sure that my responses are anonymous as I do not believe the course was instructed well and I do not want this to impact my grade.