Absolutely - but apporach it as a question, as PPs have said, not: "you're wrong", but "I heard this... and thought..., what do you think?"

I actually think that it is VITAL that you tell him. He is teaching others who don't know. If you don't tell him, he will unkowingly spread incorrect info. That is not fair to him or to any other students.

GL.

I have corrected a lecturer once. I found a mistake in the course handbook, so made an appointment to see him about it and said "can you explain this bit, it doesn't make sense...", which made him realise that it was an error. He really appreciated it, as this way he told other students in the course about the mistake before anyone else had had a chance to be misinformed.