Question 1

Which average should I use?

Accepted Answer

Use the mean for roughly symmetric numerical data, the median when there are outliers or strong skew, and the mode for categories or for the most common value.

Question 2

Can a list have more than one mode?

Accepted Answer

Yes. A list with two equally frequent values is bimodal, and the calculator lists both.

Question 3

Does the mean have to be one of the values?

Accepted Answer

No. The mean of 1 and 2 is 1.5. The median of an even-sized list can also fall between values.

Your numbers