
Mean for grouped data
I understand that when finding the mean for grouped data,
with class interval, e.g. $\displaystyle 0 \le x < 5$, we use the midpoint of the interval, then multiply by frequency, and so on...
My question is this,
If x is discrete, for the range $\displaystyle 0\le x < 5$, then x takes values 0, 1, 2, 3, 4. Should we choose 2 for the midpoint? or 2.5?
Which one better?
Thanks!!!

In this case the range http://www.mathhelpforum.com/mathhe...3e7f2d4c1.gif is actually equal to 0 < x < 4 (those should be less thanorequal signs but not sure how to do them on here), and the midpoint of that range is 2. So use 2.