Perhaps more comprehensive to show all data and only certify some of it ?
Each processor of data can make up mind at that point what data to include.
Correct. However, you have to present some rounded numbers, even only in the title of the presentation - so, at some point, you have to decide which data to include to the calculations required for the statistics...
Nowadays there are many software packages ( and many of them are free ) where one can insert all the data he has, push "Enter", and, abra cadabra,
see !

Oftentimes, we need to specify the probability distribution we expect our data to fit in... I have read that, concerning tests of the MTB of rods, ropes and wires, the best practice is to use the
Weibull distribution ( or "weak-link distribution" ):
http://en.wikipedia.org/wiki/Weibull_distribution Of course, with enough data, the pattern of distribution, if it exists, will manifest itself ! And it may be an atogether different one - which we will then name : "
The Knot Strength distribution " !

But testing is just a guide anyway.
The best/extended position of a lacing, to capture with least deformation and least impact of change in real life;
might not be testable because lacing would compress before breaking.
- or before slipping / sliding...
True... However, regarding "tight hitches" at least, where the force of the pre-tightening is important, I think that we can "solve" this, by specifying the load by which the ends(s) are pulled, before the final test and measurement of the load under which the hitch will open up, or slide, on the pole.
There are
many things that we can not yet test and measure in practical knots - and even some that we can not even imagine how to measure ! ( like the "easiness to untie a knot", for example, discussed in another thread ). However, this should not mean that we should abandon any tests and measurements, and claim whatever crosses our mind !
I believe that, in the ripe phase the study of knots has reached, it is paramount to have NUMBERS, collected by careful and repeatable tests. Otherwise, the commercialization of the knotting literature in the web, where anybody tries to gain some $ by selling
knotting myths, would accelerate ! A certain mediocre knot seller comes and claims that a certain mediocre knot based on an overhand knot tied on the Standing Part is as "easy to untie" as the Zeppelin knot, or the bowline - how on earth are we going to confront this ?