Variation is a second-order stereological parameter.

The primary goal of unbiased stereology is to make sample estimates of first-order population parameters, e.g., number, volume, length, and surface area; and, to estimate their variation.

Two important benefits arise when bias is successfully eliminated from stereological designs.

1. Accuracy - analysis of more individuals causes sample estimates to converge on the expected value of the population parameter.
2. Partitioning observed variance into its random error, which consists of biological variance and sampling variance (error). The unbiasedness of the methods allows for optimization of sampling for maximum efficiency, and thus minimizing time, labor, and material expenses.