Kvartiilivälinä

Kvartiilivälinä, often referred to as the interquartile range (IQR) in English, is a statistical measure of dispersion. It represents the range between the first quartile (Q1) and the third quartile (Q3) of a dataset. In simpler terms, it encompasses the middle 50% of the data when the data is ordered from smallest to largest.

To calculate the kvartiilivälinä, one first needs to determine the median of the dataset. The first quartile (Q1) is the median of the lower half of the data (excluding the overall median if the dataset has an odd number of observations). The third quartile (Q3) is the median of the upper half of the data. The kvartiilivälinä is then calculated as the difference between Q3 and Q1: IQR = Q3 - Q1.

The kvartiilivälinä is a robust measure of spread because it is not affected by extreme values or outliers in the dataset. This makes it a useful tool in exploratory data analysis, especially when dealing with skewed distributions. It is often used in conjunction with the median to describe the central tendency and variability of a dataset. Box plots, a common visualization tool, prominently display the kvartiilivälinä as the length of the box.