This survey accompanies my 'Satiable Curiosity column "Generation Gaps: A Sign of Microdeletions?" in the Journal of Genetic Genealogy. Please read the entire article before completing the survey.
Most parent/child comparisons show a long continuous matching segment spanning the entire length of each chromosome. Occasionally this segment is split by a small gap, due to some mismatches between the parent and child. The purpose of this survey is to explore the way these gaps are presented at various sites (Family Tree DNA, 23andMe, and GEDmatch; AncestryDNA uses a different approach and numbers are not comparable). Some gaps are patched by tolerating an occasional mismatch, but different rules are used.
David Pike's utility http://www.math.mun.ca/~dapike/FF23utils/pair-discord.php will list all mismatches without filtering them. Thus the most informative responses will compare Pike's numbers with other sites. Three different methods are offered: eyeballing the output on screen, or pasting the output into the survey, or pasting the output into a spreadsheet (available as a supplement to the column).
However, the author appreciates that this requires extra effort, and data without this information will still have much utility for looking at the effect of age and gender.
The optional GEDmatch numbers may be used in the future to identify multi-generation samples to see if some gaps are inherited.