Range and interquartile range
Using the example of point counts in a quiz, I explain how to calculate two measures of variation: range and the interquartile range. The range is the difference between the maximum and the minimum values in the data. To calculate the interquartile range, we first find the median and the 1st and 3rd quartiles (which divide the data into four parts). The interquartile range is the difference between the 3rd and the 1st quartiles. We can see that of the two groups of students, the 2nd group has much more variation in their quiz results.
See also
Mean Absolute Deviation — video lesson
Math Mammoth Grade 6 curriculum
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