Calculating the Standard Deviation of Grouped Data
The following equation shows how to calculate the standard deviation of grouped data in a frequency distribution.
fi = the number of data values in each frequency class
m = the number of classes m
= the total number of values in the data set
The following table is a frequency distribution that represents the number of times each child in Debbie’s 3-year-old preschool class needs a “potty break” in a day.
In this example, m = 5 and n = 30. From Chapter 4, we know the mean ...