@marvin100 : Nothing like people alluding to the fact that students tend to often let the personality traits of the instructor along with their difficulty/expected grade to dominate ratings. I honestly suspect that the written portion, when offered is useful. However the bubblesheet portions offered by most schools are sketchy to say the least. Some students will randomly give all high marks when the teacher may only be “decent”, but they want to hurry up and leave the classroom. Others may give low marks if they were very challenged in the course. Some instructors announce in advance that they will be having evals. the next class, and then many students skip (and then these are ones that care less or perhaps would give lower ratings). Many will not give a heads up and students will show up like it is another day of class, so they get much higher participation rates.
The participation issue is certainly an effect in large lecturers. In smaller classes, maybe not so much as students don’t want to be noticed as skipping.