Kvartiileja

Kvartiileja, often translated as quartiles in English, are statistical measures used to divide a dataset into four equal parts. They are particularly useful for understanding the distribution and spread of data. The first quartile, denoted as Q1, represents the 25th percentile, meaning 25% of the data falls below this value. The second quartile, Q2, is the median, representing the 50th percentile, with half the data below and half above. The third quartile, Q3, is the 75th percentile, indicating that 75% of the data lies below this point.

To calculate quartiles, the data must first be arranged in ascending order. The median (Q2) is found by identifying the middle value. If the dataset has an odd number of observations, the median is the single middle value. If there's an even number, it's the average of the two middle values. Q1 is then the median of the lower half of the data (excluding the median itself if the dataset has an odd number of observations). Similarly, Q3 is the median of the upper half of the data.

The interquartile range (IQR), calculated as Q3 - Q1, is a measure of statistical dispersion, representing the range of the middle 50% of the data. It is less sensitive to outliers than the total range of the data. Quartiles are a fundamental tool in exploratory data analysis and are often visualized using box plots, which clearly depict Q1, the median, Q3, and any potential outliers. Understanding quartiles helps in summarizing large datasets and identifying key points within their distribution.