Kvartilisköz

Kvartilisköz is a term used in statistics to refer to the interquartile range. The interquartile range is a measure of statistical dispersion, which is the spread of a set of data. It is defined as the difference between the 75th percentile (also known as the third quartile) and the 25th percentile (also known as the first quartile). In simpler terms, it represents the range of the middle 50% of the data.

The calculation of the interquartile range is straightforward. First, one must sort the dataset in ascending order. Then, the first quartile (Q1) is found, which is the median of the lower half of the data. The third quartile (Q3) is the median of the upper half of the data. The kvartilisköz is then calculated as Q3 - Q1.

The kvartilisköz is a robust measure of dispersion, meaning it is less affected by outliers than the standard deviation or the range. Outliers are extreme values that lie far from the other data points. Because the interquartile range focuses on the middle portion of the data, these extreme values do not significantly influence its value. This makes it a useful statistic for describing the spread of skewed data or data with potential outliers.

In descriptive statistics, the kvartilisköz is often reported alongside the median. This pairing provides a more complete picture of the data's distribution than just reporting a single measure of central tendency or dispersion alone. For example, a dataset with a small kvartilisköz indicates that the middle 50% of the data points are clustered closely together, suggesting low variability in that central range. Conversely, a large kvartilisköz indicates that the middle 50% of the data points are more spread out, suggesting higher variability in that central range.