The Black Box problem

For many people stereology is a black box. Most people do not understand what is required but are able to enter some numbers and then see one or more numbers spit out by the black box.

Consider the follow simple problem. There is a tract of land with trees on it. A question that can be asked of the trees is the mean diameter of the trees. The method selected to determine mean diameter is to wrap a tape around the tree and to read off the length. This is the perimeter of the tree trunk. Divide that by pi to obtain the mean diameter of the tree trunk. Another way to do this is to make a tape measure that is in units of pi. At pi centimeters write 1, at 2pi centimeters write 2, and so forth to make a tape where the measurements taken do not require the additional step of dividing by pi.

This sounds all well and good. There is a problem.

This simple stereological procedure does not provide the mean diameter of the tree trunk.

The value that is measured here is always greater than the mean diameter except in the case of a circle.

If you buy a tape for forestry it is marked as described above. It provides a measure of the tree. Should that tape claim to provide a measure of the mean diameter and you did not know better then you would move forward with the wrong understanding of the measurements being taken.

The same applies to other products that provide stereological results. Do not treat them as a black box. Understand what needs to be done. Use a spreadsheet of your own making to check the results of the product. Check the computed results. Make sure that the inputs are what is required. Do not trust the protocols provided by automated equipment. Independently verify that the protocols are correct.

Failure to understand stereological protocols can be a problem. Articles have been published that had to be withdrawn because the work was done without the researcher having taken the time to learn stereological methods.