this is one of those comments I frequently hear and each time wonder what it really means.
Pulled from another thread
- Thread starter SUNRAY
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[ Firstly, apologies for two 'typos' - firstly the missing "r" in what should have been "closer" and, secondly (and goodness knows why I did this!) it should be "six times", rather than "four times"! ]
As I imagine you probably understood in this case, had I typed this correctly, what it would have "really meant" was that 150mm is "six times" 25mm - i.e. that switches & sockets were allowed 6 times closer to gas pipes than other electrical things. Would you perhaps regard it as clearer had I written that the separation for switches etc. was allowed to be "one sixth" of that for other things?
Having said that, there are certainly situations in which statements about ratios, proportions and percentage differences/changes are worded in a way which can be ambiguous, due to uncertainty about the denominator which has been used. This is probably at its worst with 'percentage reductions', and at its very worst with things like "100% reduction". I think that nearly always actually means (is intended to mean) an actual 50% reduction (rather than a true '100%' reduction 'to zero') but at least it is usually obvious from context that it is not intended to mean a reduction to zero.
The worry (and perhaps uncertainty) then is that if someone might (incorrectly) say "100% reduction" for a reduction from, say, 10 to 5, one has to wonder how they would describe, say, a reduction from 10 to 8 - would they (correctly) call it a '20% reduction' or (incorrectly) as a '25% reduction'?
, differences
Although I suppose I can understand your uncertainty, I don't personally find it hard understanding that sort of form of words. The real
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I don't know what thread it was pulled from, but I can see the problems with 150%, the first time I came across it, was running and engine on two fuels to calibrate the engine, and we then ran it with a fuel under test to see when knocking started, and quoted the percentage of Octane it was equivalent to, and if the screw went past the 100% calibration point we could get over 100%.
We see something similar with heat pumps, where we consider if it is putting twice as much heat from outside into a home as we would get from a resistive heating system this is 200% again no real other way to compare.
But with other items, these comparisons are very confusing, if I was getting 90 lumens per watt from a fluorescent fitting, and I am getting 110 lumens per watt from a LED replacement, I can see how a 58 watt fluorescent is replaced by a 47.5 watt LED, so we label the 47.5 watt LED as equivalent to 58 watt. But the problem is a 58 watt fluorescent with a wire wound ballast uses more like 62 watt, and with an electronic ballast 55 watt, and also with a wire wound around 80 lumen per watt, and with an electronic 95 lumen per watt. So the equivalent depended on if compared with a wire wound or electronic and since we stopped using wire wound, it should have been compared with the electronic version.
The same with bulbs, we swapped our 60 watt bulb for an 11 watt compact fluorescent lamp (CFL) so seems good idea to mark the CFL as equivalent to 60 watt, when the LED came out again we could reduce the watts, so a 6 watt LED gives the same output as an 11 watt CFL, so to mark as equivalent to 11 watt makes sense. But by time we got the LED the tungsten lamp was just a historic item, like the carbon filament and arc lamp. So no point comparing to tungsten.
The major problem was switch mode power supplies with extra low voltage bulbs, and using bulbs which did not draw enough current would cause them to close down, And often the equivalent wattage was in larger numbers to true wattage, causing complete failures of the lamp.
This time of the year, tungsten lamps are 100% efficient, if we put 60 watts in, we get 60 watts out in heat and light, and since we need the heat, it is not wasted, but of course gas or oil is cheaper per kWh to electric, so money wise better to use gas or oil for heating. And really, when working out how efficient, we need to include time.
So if one needs to turn on one form of heating 3 hours before required, and another form 20 minutes before required, the fast one will not allow as much heat to escape, so it may need 2 kWh to heat up in 3 hours, but only 1.5 kWh to heat up in 20 minutes. But the efficiency will depend on how long it is used for, if we consider the 20-minute version as zero loses, and we need 0.5 kWh to maintain the temperature, then for 1 hour use, 2/2.5 = 80% but run it for 5 hours, then 4/4.5 = 89% efficiency.
So if we compare under floor heating and radiator heating and fan assisted radiator heating, All putting 100% of the heat into the room, but the fan assisted for a short time works out cheaper. But as one extends the time, the fan pushes air against the cold walls, where standard radiators less so, and underfloor heating does not cause an air flow, so wall can stay cool, but room is warm.
And when one looks at inferred heaters aimed where we sit, then it gets even harder to work out efficency.
In the main we don't care how efficent it is, we just want to reduce costs. I can't use this PC with gloves on, but I can with a coat on, so minium temperture is down to how warm my hands feel. And I use the kitchen for such a short time, if the living room is warm enough, rest of rooms in house hardly matter.
We see something similar with heat pumps, where we consider if it is putting twice as much heat from outside into a home as we would get from a resistive heating system this is 200% again no real other way to compare.
But with other items, these comparisons are very confusing, if I was getting 90 lumens per watt from a fluorescent fitting, and I am getting 110 lumens per watt from a LED replacement, I can see how a 58 watt fluorescent is replaced by a 47.5 watt LED, so we label the 47.5 watt LED as equivalent to 58 watt. But the problem is a 58 watt fluorescent with a wire wound ballast uses more like 62 watt, and with an electronic ballast 55 watt, and also with a wire wound around 80 lumen per watt, and with an electronic 95 lumen per watt. So the equivalent depended on if compared with a wire wound or electronic and since we stopped using wire wound, it should have been compared with the electronic version.
The same with bulbs, we swapped our 60 watt bulb for an 11 watt compact fluorescent lamp (CFL) so seems good idea to mark the CFL as equivalent to 60 watt, when the LED came out again we could reduce the watts, so a 6 watt LED gives the same output as an 11 watt CFL, so to mark as equivalent to 11 watt makes sense. But by time we got the LED the tungsten lamp was just a historic item, like the carbon filament and arc lamp. So no point comparing to tungsten.
The major problem was switch mode power supplies with extra low voltage bulbs, and using bulbs which did not draw enough current would cause them to close down, And often the equivalent wattage was in larger numbers to true wattage, causing complete failures of the lamp.
This time of the year, tungsten lamps are 100% efficient, if we put 60 watts in, we get 60 watts out in heat and light, and since we need the heat, it is not wasted, but of course gas or oil is cheaper per kWh to electric, so money wise better to use gas or oil for heating. And really, when working out how efficient, we need to include time.
So if one needs to turn on one form of heating 3 hours before required, and another form 20 minutes before required, the fast one will not allow as much heat to escape, so it may need 2 kWh to heat up in 3 hours, but only 1.5 kWh to heat up in 20 minutes. But the efficiency will depend on how long it is used for, if we consider the 20-minute version as zero loses, and we need 0.5 kWh to maintain the temperature, then for 1 hour use, 2/2.5 = 80% but run it for 5 hours, then 4/4.5 = 89% efficiency.
So if we compare under floor heating and radiator heating and fan assisted radiator heating, All putting 100% of the heat into the room, but the fan assisted for a short time works out cheaper. But as one extends the time, the fan pushes air against the cold walls, where standard radiators less so, and underfloor heating does not cause an air flow, so wall can stay cool, but room is warm.
And when one looks at inferred heaters aimed where we sit, then it gets even harder to work out efficency.
In the main we don't care how efficent it is, we just want to reduce costs. I can't use this PC with gloves on, but I can with a coat on, so minium temperture is down to how warm my hands feel. And I use the kitchen for such a short time, if the living room is warm enough, rest of rooms in house hardly matter.
(here)
When used in the correct manner, there's nothing wrong, conceptually, with percentages greater than 100%. To say, for example, that the cost of gas is " 250% " of the cost of electricity is obviously no different from saying that gas costs 2.5 times more than electricity.
However, in many contexts (when one is talking about proportions/percentages 'of a whole'), percentages greater than 100% are obviously impossible, hence meaningless. If one is talking about, say, the percentage of the weight of a human body which is accounted for by fat (or water, or whatever), it obviously cannot be more than 100%.
One of the most common potential problems arises in relation to percentage changes/differences if people use the wrong wording. To say that the price of gas has "increased TO 150% over the past X years" is obviously very different from "increased BY 150% over the past X years" - since the former means that an initial price of, say, 20 p/kWh will have increased to 30 p/kWh, whereas the latter would mean that it had increased to 50 p/kWh.
I don't get hung up on errors/typos unless it obviously changes the meaning or done by a know nothing idiot. Neither apply here
Yes very much so. Six times further than 25mm is very concise and irrefutable, whereas six times closer than 150mm is fundamentally indefinable.
I'll start by saying this is not a pop at you and generally I'll accept such comments as a very cack handed way of describing a fractional reduction of something if it makes sense.
A little while ago I heard 2 people on the London tube discussing difference between 3 times as cheap and 3 times cheaper and they both came up with very different meanings to both... none of which made any sense to me other than the previous para. They tied themselves up in so many knots that they described 25%, 30%, 1/3, 2/3, and I think they would have arrived at 50% if another hadn't joined in and started explaining a 30% price reduction followed by a 30% rise took it back to the original price as a proof it would mean both expressions meant a price reduction of 30% (to final price of 70% rather than 30%) although actually in their confusion thought it meant 1/3 = 30%.
Disturbingly I've seen a TV advert describing the special offer sale price of a bed being 5 times cheaper (I suspect this is where x times cheaper etc originated - as a means to confuse the uneducated) – original price of £999.99 down to £499.99. In the small print which I was just able to read with the VHS on pause it indicated it had been on sale in a particular store at the higher price between certain dates followed by the list of 4 other locations, prices dropping by £100 each time and dates in various sales - making this the 5th time it's cheaper.
3 times dearer makes plenty of sense; an object 3 times dearer than £10 is £30 making the operand £10 and the operant 3, by that reckoning 3 times cheaper would be reducing the price by £10, 3 times or to -£20 effectively turning the sale to a donation including a cash amount... Well that's according to the book of Sunray, others opinions may vary
Absolutely and I recall 2 of our teachers at school having opposing opinions on the topic
And that was the stumbling block between the 2 teachers.
Yes. Some are unable to understand that distinction and knowing a reduction of 50% also means to 50% will expect that to apply for any other figure IE: a reduction of 10% also means to 10% rather than the correct figure of 90%. They would expect a "25% reduction sale" to mean final prices of 1/4 of original rather than 3/4, but I've also known it to mean 25% of stock reduced in price (possibly with small print price reduction of something different to 25% and maybe variable across products) and when the tills established the stock level had been reached the discount stopped being applied.
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10% reduction of £100 = £90 and a further 10% = £81 not £80 seen this done a lot.
This is quite an interesting discussion for me since, over the years/decades, a fair bit of my work has related, directly or indirectly to the abuse/misuse of statistics (in the broadest sense), be it deliberate or 'accidental' (through ignorance) - and such abuses/misuses very often involve 'percentages'. The perpetrators are most often 'the media', politicians, business leaders etc. or 'pressure groups', but also sometimes people/organisations who/which really ought to know much better!
Does your concern only relate to situations in which proportionate changes are expressed as percentages, rather than fractions/ratios? In other words, would you be happy with "decreased by half", "decreased by one third" etc.?
Oh dear! That is definitely a case of 'mathematical ignorance'
Sure, but that's just incorrect maths, and is nothing to do with expression of the changes as percentages. A 'halving' followed by a further 'halving' takes one down to a quarter (of the original figure), not zero
One of those teachers presumably didn't understand the difference between situations in which "100%" represented an absolute upper bound, which could not be exceeded (usually because it represented 'the whole' of something, and one can't have more than 'the whole!) and other situations in which "100%" merely represents a present/past figure which may well be exceeded
You're talking there of situations in which, deliberately or otherwise, language is being used which simply isn't clear enough, to anyone. In contrast, a mathematician or otherwise reasonably numerate person would see nothing ambiguous about, say, "a 25% reduction", since they would assume that that language was being used correctly.
I've also known a man try to take a building society to task over interest payments on a fixed rate mortgage. His standing order was set up to be paid 3 monthly despite the agreement being monthly, accordingly the annual statement showed the interest amount applied each month (presunably based on daily calculations) rising then the monthly repayment increased to cover it.
Why did he set up a 3-monthly Standing Order if the agreement was to pay monthly? Unlike the situation with Direct Debits, with Standing Orders one can dictate exactly how much will be paid, and when (how often).
I know a fair bit about statistics and how they can be manipulated to give very different reports depending on the preferred point of view.
Not in the slightest, I'm sure you noticed how I slid between them
Oh yes, that was just about as far as my time on the tube allowed so I often wondered where their various incorrect thoughts led them.
Indeed. As I said, dealing with such aspects of abuse/misuse of statistics has been a significant part of my working life for decades!
Given that you are responding to quotes of two of my sentences (which probably have essentially 'opposite' answers) could you perhaps clarify what you are saying? In other words, are you happy with, say, "decreased by one third"?
No idea, however back then many things were done on a quarterly basis; energy, rates etc
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