APA Dictionary of Psychology

a measure of central tendency calculated for k numbers x₁…x_k as (x_1× x_{2 ×} x₃…x_k)^1/k. A geometric mean is similar to an arithmetic mean except that the latter involves the sum of the quantities divided by the number of quantities, whereas the former is the product of the quantities with the product raised to the power of 1 divided by the number of quantities. Thus, for the numbers 1, 2, and 3, the arithmetic mean is 6/3 = 2, and the geometric mean is the cube root of (1)(2)(3) = 6^1/3 = 1.817. See also harmonic mean.