When researching new drugs and treatments they sometimes need to know how much pain the patient is suffering.
There is no real way of finding this out to an accurate degree medically, as heart rate, reactions etc while affected by intensity of pain are very varied to begin with from person to person.
So they use a questionaire in a lot of cases, for example the patented 'McGill Pain Questionnaire' or the pictured 'wong-baker FACES scale'.
This allows sufferers to rank pain. Some from one to five, others up to twenty.
(Many of you will probably see where I am going with this now)
The doctors are under no illusion that one persons '2' will be less painful than one other persons '4' all the time without fail.
What they DO accept however is that if on average a treatment results in figures from 1-2 that it is less painful than a treatment that results in a 3-4 and the accuracy of this goes up with each new participant in the trial (so it would be more accurate say if 20 thousand people took part instead of the thousand or so in most medical trials)
Now to bring elections back into it.
Can an individuals 4th choice be guaranteed to have less support than someones 2nd? The simple answer is no..it is more likely but cannot be relied on. However, 1000 4th preferences suggest almost beyond doubt that it has less support than 1000 2nd preferences.
The law of averages is a marvellous thing you see, trusted by among many sectors, the medical profession.
If it is good enough to make life saving decisions, surely it is enough for life changing decisions like the election.
Supporters of AV will say that 1000 votes is a 1000 votes no matter how much support those votes have.