Worked example 3 The following is a list of the ages of people living in an apartment building. 21, 14, 30, 28, 17, 27, 10, 19, 17, 26, 29, 20
Find the median age of the people in the building. Solution
The median doesn’t have to be an actual value within the data set.
Mean
The most commonly used average is the mean. To fi nd the mean of a set of numbers we add up all the values and divide by the number of values. Mean = sum of the values
_____________ number of values
Worked example 4 Find the mean of the following set of numbers. 34, 10, 9, 13, 34, 15, 18, 7, 35, 22
Solution
The means doesn’t have to be an actual value in the data set.
To fi nd the mean of a frequency distribution table, we add up the frequency multiplied by the values and divide by the sum of the frequencies.
Mean = sum of ( frequency × value ) ___________________ sum of frequency
We encountered frequency distribution tables in Section B, Unit 18.