The arithmetic mean describes the average trend of a set of data and is the sum of all data divided by the number of data. When used in statistics, it should be noted that the arithmetic mean cannot be calculated when extreme values, ambiguous data or data of different qualities are present.
The average age of residents in a community was calculated, including 204 children under 10 years old and 26 old people over 90 years old is suitable for calculating the arithmetic mean according to the above definition.