interkvartiilivahemiku

Interkvartiilivahemik, often abbreviated as IQR, is a statistical measure that represents the range of the middle 50% of a dataset. It is calculated by subtracting the first quartile (Q1) from the third quartile (Q3). The first quartile is the value below which 25% of the data falls, and the third quartile is the value below which 75% of the data falls. Therefore, IQR = Q3 - Q1.

The interquartile range is a robust measure of statistical dispersion, meaning it is less affected by extreme values or outliers compared to the range (maximum value minus minimum value). This makes it a useful tool for understanding the spread of data, especially when the data might contain outliers that could skew other measures of variability.

In practice, the IQR is often used in conjunction with the median to describe the central tendency and spread of a dataset. A box plot, for example, visually represents the IQR as the length of the box, with the median shown as a line within the box. A larger IQR indicates greater variability in the middle 50% of the data, while a smaller IQR suggests that the middle 50% of the data points are clustered more closely together. The IQR is also a key component in identifying potential outliers, which are often defined as data points that fall below Q1 - 1.5 * IQR or above Q3 + 1.5 * IQR.