Systematic Random Sampling

A systematic random sampling (SRS) is an unbiased, efficient sampling technique. It is preferable to other forms of sampling when multiple sampling runs are implemented, either for a given region of interest, or for several regions of interest when multiple tissue groups are examined.

  • Once the shape and size of a sampling area or volume is chosen and a region of interest has been defined by drawing a contour around it, sampling sites are evenly distributed throughout the region of interest.
  • The distribution pattern of the sampling sites is systematic (i.e., the distance from one sampling site to the next is constant).
  • The placement of the pattern of sampling sites is a random component.

If a region of interest is sampled more than once (or if a series of similar regions of interest are sampled), the sample area/volume at each sample site and the distance between the sample sites do not vary. But the placement of the systematic sampling scheme for each sample run is randomized.

Systematic random sampling of serial sections

This consists in defining a random selection process to select a small number of uniformly spaced sections from a complete sequence of sections.

You need to determine the exact number of sections to sample and the section increment based on considerations about estimation precision (see Determining sampling precision).

  • The section increment is systematic.
  • The choice of the first section sampled is random.

Example: The number of sections to sample is 30 and the section interval is 4. The first section sampled is a random selection of 1, 2, 3 or 4.

When you sample several series of sections, randomly select a new starting section for each series, but use the same section increment for all the series.

To set up a systematically random sample of serial sections

  1. Define your sections with the Virtual Section Manager
  2. In the Serial Section Setup dialog box :
    • Define the parameters as needed.
    • To select the first section to sample, click Pick Random OR enter a section number if you have already done the randomization.

If you plan to use a workflow, these steps are unnecessary.

 

See Preview SRS Layout