1. What is the disadvantage of using the median as an average for a set of scores?

It does not give any indication of the extreme small or large values or the range of values.

2. If a value in a set of data is 0, is it counted when working out the mean?

Yes, when working out how many values there are the 0 must be counted.

3. Can a calculator work out the median of a set of values?

The latest calculators can find out just about anything, including the median.