We all know that the ASA have a big issue with someone saying that broadband can be "up to 80Mb/s". They need it dumbed down to a 90th percentile or some such.
Indeed, even OFCOM want a "range" of speeds on an individual line estimate, but rather than a range of the "lowest speed we would ever expect without a line being faulty" to "the highest speed physically possible on that line length", they actually want 20th to 80th percentiles, to dumb it down, and create a case where 40% of people see line speeds that are not in the "range" that was quoted.
So, some simple bits of logic here, which any scientist or engineer will understand.
If I quote a simple single figure for something, such as 100mm, there has to be some tolerance for that. E.g. let's say I am telling you the length of a metal rod that is to be used as a part in some machine.
You cannot make a metal rod that is 100mm long. Basically, at the edge of that rod will be atoms, and at the very best you can make it one atom more or one atom less in length, and even the "edge of the atom" is questionable. If 100mm is not an exact number of atoms long, you have not made a rod 100mm long. It is just close, even if very very very close...
In practice I may say 100mm ±1mm. This creates a range of 99mm to 101mm. You can aim for that, and will meet it or not.
Whatever analogue metric you are quoting, length, temperature, voltage, as a fixed value, ultimately it has to have a tolerance. It should all be explicitly stated, though some specification may say "all lengths are ±1mm" or some such. In any case you need to know the tolerance to understand the fixed value you are given.
Very similar to the above, any measured analogue quantity will have an error margin, and it is just like a tolerance. If you say it is 20℃ in here, then that will have a margin, maybe ±0.5℃
If you specify a limit, e.g. a minimum, or a maximum, or a range, you do not need a tolerance.
A limit can be absolute. E.g. that metal rod must be <100mm. A rod that is one atom longer is not within limit.
Some of you may have seen my example label for the new FireBricks. Based on the specs of the parts we quoted 85V-264V AC. That is a range.
These limits are absolute, 84.9999V is too low, 85.00001V is fine (as it 85V).
But guess what? The figures we quote have to allow for 10% tolerance. WTF? Limits do not need tolerances, they are absolutes.
End result, we have quoted 100V-240V. The 240V with 10% is 264V. The 100V with 10% off is 90V not 85V, but we can handle down to 85V. We decided to give in to the madness as say 100V. We could have gone for 110V maybe. The same issues with frequency of supply, a range but with a tolerance on the values?!?!
But really, what is wrong with actual limits - why is this remotely hard - limits do not need tolerances.
As an engineer I would read that as 241V is too high, but apparently that is not the way the regulations work!
P.S. I saw a strange use of ± on train times, I think in Holland, but not sure. Basically they would say train due in ±5 minutes, when they definitely did not mean due -5mins. They actually means 5mins ±something, but was a strange way to quote it. It was almost as if they used ± as "about", when it means "plus or minus". Using ~, e.g. train in ~5mins, would make a lot more sense as "about 5mins".