# Geometric Mean

The geometric mean is often used to describe the center of a set of numbers that are right-skewed, such as the C-reactive protein values of participants in a cohort study. It is calculated by first taking the logarithm of each number, calculating the arithmetic mean, and then taking the antilog. The median is also used for similar purposes. The geometric mean is usually preferable when quantitative analyses of the numbers are done with logarithmic transformation, because the median has less relation to such analyses. The median is usually used when nonparametric analyses are performed.