jmc

The mean, or average number of days is the total number of days divided by the total number of students. The total number of days is $1\cdot 1+2\cdot 3+3\cdot 2+4\cdot 6+5\cdot 8+6\cdot 3+7\cdot 2=109$. The total number of students is $1+3+2+6+8+3+2=25$. Hence, $\frac{109}{25}=\boxed{4.36}$. This problem is a good example of times when the problem statement may give information that may seem important to solving the problem, but turns out it's just there to mess around with you. In my opinion, I think that it's not a good example of that.