08 Jun 22
@sonhouse saidRight. But can you *end up* at a percentage that is less than zero? Obviously you can subtract 10 percent from a whole; but can you actually *arrive* at a total remaining percentage that equals a negative?
@vivify
Of course there can be either when it comes to money, you buy at 100, sell at 50, you have a minus 50% profit, or a 50% loss, take your pick.
Or you buy at 100, sell at 200, 200% gain, X2,
09 Jun 22
@vivify saidA percentage is just a number and can therefore have any value. Negative a million percent for example is simple -1,000,000% = -1,000,000/100 = -10,000
Somehow I missed this post.
So by the very definition of percentages being out of 100, the idea of a negative percentage is not possible, correct?
What about the fact that percentages can be over 100 percent? Like if business had a 200 percent increase in profits? If percentages can exceed 100 percent maybe they can be lower than zero? Unless I'm missing something you can clear up.
When you talk about chances of something happening you are in the realm of probability. In math probability ranges from 0 to 1, but that is the same as 0%-100%. So the fact that it's a percentage is irrelevant.
Try to separate in your mind the idea of percentages and the idea of the chance of something happening because those are two completely independent concepts. Any example with numbers can be converted into percents.
Let's say Sumo Sam is trying to gain weight. His weight is only 200 lbs. He eats his fatty sumo rice (or whatever it is they eat) and a month later weighs himself again. He is 190 lbs!
Sumo Sam's weight increase is -5%.
@vivify saidDepends on what you're analyzing. No, you cannot have negative 50% of a cake, but it has nothing to do with the percents. It's just you cannot have negative cake at all!
Right. But can you *end up* at a percentage that is less than zero? Obviously you can subtract 10 percent from a whole; but can you actually *arrive* at a total remaining percentage that equals a negative?
But if you're measuring something that can go negative, like altitude above sea level, then whether you measure the negative as just a number (500 meters) or a percentage (50% of a kilometer) it's still possible to be negative. -500 m above sea level is 500 m deep in the water, which is also -50% of a km above sea level, or 50% of a km down into the water.
Can you have a negative number? What is an example of a negative number? This is basically the same question you are asking. What does -3 look like? Can you have -3 pairs of shoes? No...but if a shoe store lists on it's inventory that it has changed by -3 shoes because they were sold the number has real meaning.
10 Jun 22
@vivify saidOne can speak of a "-5% increase," which means a 5% decrease. But saying an event has a -5% chance of occurring has no meaning. A 0% chance of an event occurring means the event cannot occur.
Can a percentage be in the negatives, like a -5% chance of something happening? Can a percentage of a total be in the negatives?
If negative fractions exist, doesn't this imply that negative percentages also exist?
17 Jun 22
@soothfast saidIt's exactly right, like 5 - 3 is the same as saying 5 + -3. Otherwise, ATY got it right.
One can speak of a "-5% increase," which means a 5% decrease. But saying an event has a -5% chance of occurring has no meaning. A 0% chance of an event occurring means the event cannot occur.
But also, saying something has a -5% chance of occurring is just like saying that it has a 5% chance of NOT occurring. You're just moving the negative.
17 Jun 22
@athousandyoung saidMaybe on the Kelvin scale.
In fact temperature cannot equal zero either.
17 Jun 22
@vivify said+ and - are just direction, man. They have no value, they just tell you which way to go.
Somehow I missed this post.
So by the very definition of percentages being out of 100, the idea of a negative percentage is not possible, correct?
What about the fact that percentages can be over 100 percent? Like if business had a 200 percent increase in profits? If percentages can exceed 100 percent maybe they can be lower than zero? Unless I'm missing something you can clear up.
17 Jun 22
@suzianne saidThat is a curious interpretation that I, as a mathematician, have never heard of. So a -100% chance of something occurring means a 100% chance of not occurring, which in turn means a 0% chance of occurring. You've inverted the entire scale, but for what purpose?
But also, saying something has a -5% chance of occurring is just like saying that it has a 5% chance of NOT occurring. You're just moving the negative.
One could define negative probabilities in this way, perhaps, but the standard definition of the probability P of an event E restricts the possible values of P to between 0 and 1. Multiply by 100 to get a percentage.
17 Jun 22
1 edit
@suzianne saidNot surprisingly, in hindsight, there is a twig in the tree of mathematics that plays with negative probabilities, though it looks like physicists were the main driver behind it:
+ and - are just direction, man. They have no value, they just tell you which way to go.
https://en.wikipedia.org/wiki/Negative_probability
Physicists sometimes talk about "negative mass" and "negative energy," so I guess I should have expected this.
EDIT: You can read the article and let me know if the physicists' notion of negative probability jibes with yours!
17 Jun 22
@soothfast saidBut, see, a -100% chance of occurring and a 100% chance of not occurring is the same thing, resulting in a 0% chance of occurring.
That is a curious interpretation that I, as a mathematician, have never heard of. So a -100% chance of something occurring means a 100% chance of not occurring, which in turn means a 0% chance of occurring. You've inverted the entire scale, but for what purpose?
One could define negative probabilities in this way, perhaps, but the standard definition of the prob ...[text shortened]... event E restricts the possible values of P to between 0 and 1. Multiply by 100 to get a percentage.
Somehow the circle come back around on itself, to where -100% equals 0%.
But, a 50% chance of occurring is also a 50% chance of not occurring.
Perhaps I misspoke (I was always crap at math). Maybe a 5% chance of occurring equals a 95% chance of not occurring. That sounds more like it. The numbers have to equal 100, so you may be right, that -% of something occurring is nonsense.
I was trying to move beyond practical into theoretical, and it just didn't work. 🙂
17 Jun 22
@soothfast saidIt might work, but I lack the math knowledge to even ascertain if that's possible.
Not surprisingly, in hindsight, there is a twig in the tree of mathematics that plays with negative probabilities, though it looks like physicists were the main driver behind it:
https://en.wikipedia.org/wiki/Negative_probability
Physicists sometimes talk about "negative mass" and "negative energy," so I guess I should have expected this.
EDIT: You can read the article and let me know if the physicists' notion of negative probability jibes with yours!
Your Wiki link is beyond my pay grade, although the idea of + versus - in the quadratic in the denominator is interesting, but that example is from physics, so slightly easier for me to begin to "get it".
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18 Jun 22
@soothfast saidThough, from that page it seems that you can't have negative probabilities after all, only negative quasi-probabilities.
Not surprisingly, in hindsight, there is a twig in the tree of mathematics that plays with negative probabilities, though it looks like physicists were the main driver behind it:
https://en.wikipedia.org/wiki/Negative_probability
Remains the fact that it's not the percentage which is the problem, it's the probability. Doesn't matter if you express the probability out of 100% or out of 1.0, it can't go below zero. And on the other hand, doesn't matter if you measure growth in cm or in % of the original, it can go negative.