interquartile range
The difference between the first and third quartiles; a robust measure of sample dispersion.
Examples of interquartile range in the following topics:

Interquartile Range

Measures of Variability
 There are four frequently used measures of variability: range, interquartile range, variance, and standard deviation.
 The interquartile range (IQR) is the range of the middle 50% of the scores in a distribution.
 For Quiz 2, which has greater spread, the 75th percentile is 9, the 25th percentile is 5, and the interquartile range is 4.
 Using this terminology, the interquartile range is referred to as the Hspread.
 The semiinterquartile range is defined simply as the interquartile range divided by 2.

Exercises
 For the test scores in question #6, which measures of variability (range, standard deviation, variance) would be changed if the 22.1 data point had been erroneously recorded as 21.2?
 : mean, median, mode, trimean, geometric mean, range, interquartile range, variance, standard deviation
 (SL#2) Find the mean, median, standard deviation, and interquartile range for the leniency scores of each of the four groups.
 (AT#7) What are the standard deviation and the interquartile range of the d0 condition?

Practice 1: Center of the Data

Box plots, quartiles, and the median
 The total length of the box, shown vertically in Figure 1.25, is called the interquartile range (IQR, for short).

The Density Scale

Lab: Continuous Distribution

Measures of the Location of the Data

Graphs of Qualitative Data

Outliers