U-statistics

U-statistics are a way to estimate certain characteristics (like averages) of a larger population based on sample data. They are calculated by taking all possible groups of a specified size from the sample and applying a special function to each group. The average of these function values provides the U-statistic, which gives a reliable and unbiased estimate of the population parameter. This approach is commonly used in statistics because it minimizes bias and makes efficient use of data when estimating things like means, variances, or more complex measures.