Do only electronic RCD's/RCBO's have functional earths?

[EFLImpudence]

Interesting. I realise that I am biased by my background and 'the world I work in', but I would have thought that the majority of 'ordinary persons' do (whether they realise it or not) understand, accept and often use the statistical meaning of "probability" - i.e. they do understand (and use) the concept of 'low probability'. Because of the dictionary definitions, you appear to believe that a "probability" always has to relate to a fairly high (statistical) probability - is that the case?

They may understand what is meant.
Whether they think about the actual meaning of the words is an entirely different matter.

As above, I would think that the majority of the general public do understand the (essentially statistical) concept of a "low probability", which you don't seem to regard as a valid concept.

Reasonably low is fine. It is probable someone in Britain will be killed by lightning this year.
However, if something is vanishingly small or non-existent then it is not probable (likely).
There will probably be a major earthquake in London tomorrow is not correct.

I'm not quite sure what your point is. As I have said, statistical probability can be zero (or low, or extremely low), albeit usually in relation to silly theoretical cases. For example, the (statistical) probability of a dead person being alive is zero.

I've accepted that the use of probability when working on probability theory is not going to be altered to possibility below a threshold but that does not mean it is the correct use by definition.

Well, if you were using 'proper grammar', you would probably say "my", rather than "me"

Not in this case.

Notwithstanding that, I agree with you, but not for the reason you are presumably thinking of. Although there are situations in which it would be extremely improbable (e.g. if the person was an incapacitated 90 year-old), I suppose one can never say that it is totally impossible that any given person will ever go to the moon - so, in 'my' language, I would be happy for them to say that "The probability of me [my!] going to The Moon is incredibly small" - but you do not accept the concept of incredibly small (or even just small) probabilities.

I did mean in a situation where it is not going to happen - substitute Sun for Moon.

 

[bernardgreen]

if one took that viewpoint to its extreme, one would have an EICR undertaken on ones electrical installation at least once every day

Isn't that what MCBs and RCBOs do 24/7 ? They detect most faults ( the most probably and most dangerous ones ) and shut the power off. An EICR doesn't turn the power off.

Some hilltop ( wireless comms stations ) with TT supply had detection for the Neutral going above Ground. Alarms at a low voltage and disconnection of both incoming Live and Neutral if the difference went above a certain voltage. Standby generators would be used in that situation.

 

[bernardgreen]

I'm not sure that you put that into practice.

I often did. Like making the private wire taking modulation to a transmitter site to be easily used as a voice line just by plugging a voice powered phone in should an engineer need to contact the control room. This was before mobile phones. It came in handy for routine servicing ( 14 sites around London on tower blocks ) and once when someone shut and locked the roof access door not knowing an engineer was up there. Soon after that "impossible" incident BT phones were installed at several of the sites.

 

[JohnW2]

Reasonably low is fine. It is probable someone in Britain will be killed by lightning this year.

Indeed - but, by wording it in that way, you are talking about a (statistical) probability that is actually very high. It is the (statistical) probability that any given individual will be killed by lightning in any year that is exceptionally low.

However, if something is vanishingly small or non-existent then it is not probable (likely).

Again, although it is not "probable", in my language that is the same as saying that the probability is very low.

There will probably be a major earthquake in London tomorrow is not correct.

Agreed, but that is not a probabilistic statement. The probability of there being a major earthquake in London tomorrow is extremely low.

I did mean in a situation where it is not going to happen - substitute Sun for Moon.

OK in in that case the (statistical) probability really would be zero. "Zero probability" is synonymous with "impossible" (just as "100% probability" is synonymous with "inevitable").

I've accepted that the use of probability when working on probability theory is not going to be altered to possibility below a threshold but that does not mean it is the correct use by definition.

I think that we are now merely repeating ourselves incessantly. You and I exist in different (technical) worlds and hence speak somewhat different languages! However, I thought that you and others here were always saying that when 'technical definitions/usage' and 'dictionary definitions/usage' differ, people should be educated to use words correctly according to the technical definition/usage - as with (light) "bulb", for which dictionaries indicate that this word still has the meaning of what you would call a "lamp".

Kind Regards, John

 

[JohnW2]

I'm not sure that you put that into practice.

I often did.....

Did I really type that?(yes, I did!). I meant to type "I'm not sure how you put that into practice" - and have now edited my post accordingly!

Kind Regards, John

 

[JohnW2]

Isn't that what MCBs and RCBOs do 24/7 ? They detect most faults ( the most probably and most dangerous ones ) and shut the power off.

Indeed they do, but there are plenty of potentially dangerous faults that can arise at any time that are "not impossible" (even immediately after an inspection) but which would not cause any protective device to operate.

Of course we do not have our installation inspected every day because of that incredibly low risk, but if one was working on the (unrealistic) basis of trying to anticipate anything that "was not impossible", then I suppose one would have to.

Kind Regards, John

 

[EFLImpudence]

Indeed - but, by wording it in that way, you are talking about a (statistical) probability that is actually very high. It is the (statistical) probability that any given individual will be killed by lightning in any year that is exceptionally low.

In that case it is not probable that I will be killed by lightning but possible.

Again, although it is not "probable", in my language that is the same as saying that the probability is very low.
Agreed, but that is not a probabilistic statement. The probability of there being a major earthquake in London tomorrow is extremely low.

So low as to be not probable but possible (if geologically possible - not sure).

in in that case the (statistical) probability really would be zero. "Zero probability" is synonymous with "impossible" (just as "100% probability" is synonymous with "inevitable").

That is what I'm saying - although statisticians may use the term "Zero probability" it is not correct.
"Zero probability" is therefore not probable.

I think that we are now merely repeating ourselves incessantly.

That's because you keep disagreeing with me.

You and I exist in different (technical) worlds and hence speak somewhat different languages! However, I thought that you and others here were always saying that when 'technical definitions/usage' and 'dictionary definitions/usage' differ, people should be educated to use words correctly according to the technical definition/usage - as with (light) "bulb", for which dictionaries indicate that this word still has the meaning of what you would call a "lamp".

Yes, but in those cases both definitions are correct in their own way.

I admit everyone calls them bulbs and it doesn't really matter but bulb refers to the shape of the lamp.
What about calling a fluorescent tube a bulb?
I don't think I have ever 'told' anyone not to use the word bulb even though I may reply with lamp.
If people call switches sockets then I would point it out to them as it is wrong and leads to confusion.

The probability argument is because it doesn't mean what it is being used for.

Can you have "Zero Frequency"?

 

[JohnW2]

That is what I'm saying - although statisticians may use the term "Zero probability" it is not correct.

It is totally correct in terms of the technical definition of "Probability" used by statisticians.

As I've said, the general view around here seems to be that when technical and dictionary definitions/usage differ, the general public should be told/encouraged to use the correct technical term.

Even though the discussion has been about use of the word "probability", you seem to have been relying on the dictionary definition of "probable". The OED definition of "probability" (and most other dictionaries are similar) is "the extent to which something is likely to happen or be the case" - which is essentially the same as mathematical/statistical definition (and allows for small, even "vanishingly small" probabilities). Does that not render 'my' use of the word acceptable/ 'correct'?

In any event, a thought has occurred to me. Since your argument is all about the meaning of the word "probability", what if I substitued "chance" or "risk" (or even "odds", although that is mathematically slightly different), which are essentially synonymous with "probability". In other words, would you be happy if I talked of a "vanishingly small chance" or "vanishingly small risk"?

Can you have "Zero Frequency"?

That depends a bit on what you mean by "frequency" (whether in the mathematical/statistical sense, or the physics/engineering sense) but, in all cases (particularly the former) I would say that the answer is essentially 'yes'. In terms of that former meaning, if one looks at a group of people and ascertains how many of them have green skin, and finds that there are none, then the frequency of green skin in that group is zero.

Kind Regards, John

 

[EFLImpudence]

It is totally correct in terms of the technical definition of "Probability" used by statisticians.

I have accepted that the word may be misused in that sense.

As I've said, the general view around here seems to be that when technical and dictionary definitions/usage differ, the general public should be told/encouraged to use the correct technical term.

I do not accept that that applies in the case of probability - when something is not probable.

Even though the discussion has been about use of the word "probability", you seem to have been relying on the dictionary definition of "probable". The OED definition of "probability" (and most other dictionaries are similar) is "the extent to which something is likely to happen or be the case"

Yes, so, if that is vanishingly small then it is not probable.

- which is essentially the same as mathematical/statistical definition (and allows for small, even "vanishingly small" probabilities). Does that not render 'my' use of the word acceptable/ 'correct'?

I don't think so.

In any event, a thought has occurred to me. Since your argument is all about the meaning of the word "probability", what if I substitued "chance" or "risk" (or even "odds", although that is mathematically slightly different), which are essentially synonymous with "probability". In other words, would you be happy if I talked of a "vanishingly small chance" or "vanishingly small risk"?

Not really - a vanishingly small chance of something happening, by definition, means it is not probable; there is a vanishingly small possibility that it may happen.

This is where we came in.
Unless probable and possible mean the same, then you cannot logically be right.

That depends a bit on what you mean by "frequency" (whether in the mathematical/statistical sense, or the physics/engineering sense) but, in all cases (particularly the former) I would say that the answer is essentially 'yes'. In terms of that former meaning, if one looks at a group of people and ascertains how many of them have green skin, and finds that there are none, then the frequency of green skin in that group is zero.

I may give you that one.

I was thinking in the electrical sense akin to such economical terms as negative growth.

I am sure there are some classic American terms but I can't think of one now.

 

[JohnW2]

I have accepted that the word may be misused in that sense.

It is surely no more a case of 'misuse' than was the case when 'technical language' started using "lamp" to refer to things which every dictionary said was a light bulb?

I do not accept that that applies in the case of probability - when something is not probable. ..... Yes, so, if that is vanishingly small then it is not probable. ... Not really - a vanishingly small chance of something happening, by definition, means it is not probable; there is a vanishingly small possibility that it may happen. .... Unless probable and possible mean the same, then you cannot logically be right.

You seem to be missing something. It is you who brought the word "probable" into this discussion. It all started because of my use of the word "probability". That is what I have been talking about throughout and, as I have pointed out, dictionaries give a definition of "probability" which essentially corresponds to my use of the word.

Although the two words are obviously related, I think what has probably gone wrong with everyday/dictionary English, and what causes this confusion, is that, somewhere along the line, "probable" has come to mean "fairly high probability".

Kind Regards, John

 

[EFLImpudence]

It is surely no more a case of 'misuse' than was the case when 'technical language' started using "lamp" to refer to things which every dictionary said was a light bulb?

It is if they are not bulb shaped.

You seem to be missing something. It is you who brought the word "probable" into this discussion. It all started because of my use of the word "probability". That is what I have been talking about throughout and, as I have pointed out, dictionaries give a definition of "probability" which essentially corresponds to my use of the word.

...but is that not because of the "Probability Theory"?
Perhaps the whole subject should be renamed "Possibility Theory"

Although the two words are obviously related, I think what has probably gone wrong with everyday/dictionary English, and what causes this confusion, is that, somewhere along the line, "probable" has come to mean "fairly high probability".

Are you saying they used to have exactly the same meaning?
What if I reply "Possibly"?
What if I reply "Probably"?
No difference?

 

[JohnW2]

It is if they are not bulb shaped.

That is arguable, but 'technical language' started saying that "lamp" was correct, but "bulb" was incorrect, even if (as was/is often the case) the items in question were still as 'bulb shaped' as they had ever been.

...but is that not because of the "Probability Theory"? Perhaps the whole subject should be renamed "Possibility Theory".

Hmmm. You have to go back about 400 years to the time when "Probability Theory" was given its name (and with it, the meaning of "probability" that I'm talking about, which is still today the diictionary definition). You may be right that it they should have called it something different - but they didn't!

Are you saying they used to have exactly the same meaning? .... What if I reply "Possibly"? What if I reply "Probably"? No difference?

I have to repeat that, although your problem seems to be with my use of the word "probability", all your arguments are in relation to the words "probable" and "possible", which are different words. In terms of those last two words, you are right - "possible" means that probability is non-zero, but is otherwise not quantified (i.e. 'it could happen', but with no implications as to how likely), whilst "probable" means that probability is 'fairly high' ('likely' or 'fairly likely'). However, none of that has anything to do with the meaning of "probability".

Kind Regards, John

 

[EFLImpudence]

That is arguable, but 'technical language' started saying that "lamp" was correct, but "bulb" was incorrect, even if (as was/is often the case) the items in question were still as 'bulb shaped' as they had ever been.

Lamp covers all things which light; a bulb is named after its shape as is the tulip bulb.

I have to repeat that, although your problem seems to be with my use of the word "probability", all your arguments are in relation to the words "probable" and "possible", which are different words. In terms of those last two words, you are right - "possible" means that probability is non-zero,but is otherwise not quantified (i.e. 'it could happen', but with no implications as to how likely),

Yes, Possible means it is able to happen and may happen whether or not it has ever happened before.

whilst "probable" means that probability is 'fairly high' ('likely' or 'fairly likely').

That's what I have been saying.

However, none of that has anything to do with the meaning of "probability".

Probable means that [the] probability is fairly high but has nothing to do with the meaning of probability.

 

[JohnW2]

Lamp covers all things which light; a bulb is named after its shape as is the tulip bulb.

Indeed, but we are now told that it is incorrect to refer to something as a bulb even if it shape does resemble that of a tulip bulb (at least, to the same extent that many resembled tulip bulbs when we were 'allowed' to call them bulbs).

Probable means that [the] probability is fairly high but has nothing to do with the meaning of probability.

OK, I admit that I worded that fairly badly . What I was trying to say is that if you accept that 'Probable means that [the] probability is fairly high' (which you've just said is 'what you have been saying'), then that surely means that you do understand (and, more to the point, accept) the true meaning of "probability", doesn't it? If you accept that the concept of 'probability is fairly high', then I would have thought that you would also accept the concept of 'probability is fairly low' (or even 'very/extremely low').

Kind Regards, John

 

[EFLImpudence]

OK, I admit that I worded that fairly badly . What I was trying to say is that if you accept that 'Probable means that [the] probability is fairly high' (which you've just said is 'what you have been saying'),

Yes.

then that surely means that you do understand (and, more to the point, accept) the true meaning of "probability", doesn't it?

Yes, I think I do.

If you accept that the concept of 'probability is fairly high', then I would have thought that you would also accept the concept of 'probability is fairly low' (or even 'very/extremely low').

It depends how low,

I refer the honourable gentleman to the earlier post which prompted my initial comment,

The probability of losing the neutral and having an earth fault at the same time, a double fault condition, is vanishingly small – certainly so small that there is no reason to take it into account when specifying protection devices

I am never happy when probabilities are dismissed simply because they are vanishly small.

which is not a probability. It may never have happened before; it is a possibility.