In mathematics, if you want to find a simple average of the
data, you would add up the values and divide by the number
of items. This is called an arithmetic mean. This is a
straightforward calculation used with interval scales where
specific figures can be added together and then divided.
However, it is possible to mislead with averages, especially
when the range of the values may be great. Researchers,
therefore, also describe the mode which is the most frequently
occurring value, and the median which is the middle
value of the range. The mode is used when dealing with
nominal scales, for example it can show that most respondents
in your survey are Catholics. The median is used
when dealing with both ordinal and interval scales.