Kvartillid

Kvartillid is a term used in statistics to refer to a specific type of quantile. Quantiles divide a probability distribution or a sample of data into equal-sized contiguous subgroups. Kvartillid, specifically, divides the data into four equal parts. These dividing points are known as quartiles.

The first quartile, often denoted as Q1, represents the value below which 25% of the data falls. It is also known as the lower quartile. The second quartile, Q2, is the value below which 50% of the data falls. This is equivalent to the median of the dataset. The third quartile, Q3, is the value below which 75% of the data falls, and it is also called the upper quartile.

The interquartile range (IQR) is a measure of statistical dispersion, calculated by subtracting Q1 from Q3 (IQR = Q3 - Q1). The IQR represents the middle 50% of the data and is less sensitive to outliers than the total range of the data. Kvartillid are commonly used in descriptive statistics to summarize the spread and central tendency of a dataset. They are also fundamental in constructing box plots, a visual representation of data distribution.