The precision of estimates in stereological analyses.

When quantifying the total volume, number, length, or surface of morphological features in complex structures such as the brain, it is neither desirable nor feasible to make absolute determinations of these parameters. It would take a lifetime to count all of the neurons or measure the total length of dendrites in many parts of the brain. Estimates based on a relatively small number of samples of even the most complex structures will suffice, if the estimates are unbiased and have a sufficient amount of precision. It is important to have an understanding of what the precision of an estimate actually means and how it can be calculated and altered, to optimize studies with regard to the number of individuals, sections, and probes used in an analysis. An optimal sampling scheme is one that involves a minimum of sampling but still provides enough precision to draw a conclusion with a predetermined level of confidence.