Grouped frequency table: midpoint
for 8th grade

Grouped frequency tables: midpoint

Continuous data can be represented in a "Grouped frequency table" where each class (group) covers the data points within a certain range, and the classes together cover the entire range of the data.

Grouped frequency tables are useful when there are so many raw data points that discrete values would become impossible. A limitation of continuous data is that individual data points are lost so that calculations of the mean, mode or range of the original discrete data points becomes impossible. Instead techniques have been developed to approximate these values for continuous data.

The mean of grouped continuous data can be approximated by finding the midpoint for each class multiplied by the frequency of that class and adding those values then dividing by the total frequency count of all the classes.

The midpoint is calculated by adding the highest number in a range to the lowest number and dividing by 2. So if a grouped frequency table has the classes: 1-10, 11-20, 21-30, and you are asked for the midpoint of the range 21-30, the calculation is 21 + 30 / 2 which is 25.5.

In this topic you are asked to find the midpoint for a specified class in a series of grouped frequency tables. There are 8 question/answer pairs in the lessons, and an additional 8 question/answer pairs in all the games and tests.