In statistics there are three types of average: the mean, the median and the mode. Measures of spread such as the range and the interquartile range can be used to reach statistical conclusions.
The range shows how spread out the dataValues, typically letters or numbers. is. The bigger the range, the more spread out the data. The smaller the range, the closer together or more consistent the data.
The interquartile range shows the range of the middle 50% of the data.
To find the interquartile range, subtract the value of the lower quartile (the item of data \(\frac{1}{4}\) or 25% of the way through the data) from the value of the upper quartile (the item of data \(\frac{3}{4}\) or 75% of the way through the data).
The interquartile range is usually used with large data sets, cumulative frequency graphs and box plots. It is covered in more detail in Representing data.