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1, 11, 21, …, the second estimate based on the analysis of the sections no. For instance, a section-sampling interval of 10 means that every tenth section was selected, yielding 10 different estimates of the total numbers of pyramidal cells (with the first estimate based on the analysis of the sections no. Here every second section from 2 to 20 is used and estimates are repeated. In this example, an increase of the section-sampling interval causes an increase in the variability of the cell population estimates. Which of the CE estimators and associated factors (see xxx) best predict the observed variability of the subsample estimates and can be used in the assessment of estimate precision in the actual project.įigure 1 demonstrates the effect of the sampling scheme on the variability of estimates of the total number of cells using the Optical Fractionator.Which sampling scheme is returning a precision suitable for the purpose of the study.The size and variability of the calculated CEs for a range of sampling intervals, and.How much the estimates actually fluctuate with changes of the sampling intervals, i.e., we obtain a statistical sample of the ‘true’ CE.The subsample estimates allow us to evaluate: From this larger sample, subsamples can be drawn corresponding to 2, 1, 0.8, 0.66, 0.57, 0.5 … times the originally intended sampling density in terms of sections or probe placement or combinations thereof. If it is judged that, e.g., every n th section would seem appropriate and that probes should be placed at m um x, y-intervals, one may decide to sample two or three animals with, e.g., every ¼ n thsection and with ½ m um intervals. This “starting scheme” is at least a good beginning for a more rational study design. The choice of sampling parameters often depends on a sufficient knowledge of the structure of interest, which can not be substituted for by stereological theory.
#CAVALIERI COEFFICIENT OF ERROR FOR STEREOLOGY FREE#
Sampling schemes which are free of these faults are good “starting schemes” and will often, when formally assessed using CE estimators, typically return methodological contributions to variance which are ‘good enough’ and often ‘better than necessary’. The oversampling-subsampling approachįew investigators would be comfortable with a the idea of using a sampling scheme in which the selected sections frequently miss important anatomical features of the structure of interest, and in which probes rarely ‘hit’ the objects whose properties are to be estimated.
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There are several recommended schools of thought into how much work should be done to achieve a desired level of accuracy. ‘How many probes should I place in how many sections?’ is a frequent question that ‘stereologists’ are confronted with – and one that they often are less qualified answering than the person asking.