Can't believe nobody has linked the relevant xkcd yet

Having two possible outcomes does not mean it's a 50:50 chance.

"So if I aim the arrow at the 1cm square from 100m away and shoot, I either hit it or I don't. So basically I have a 50% chance of hitting it."

That's not even a stat question, it is a english question. It is an increase by 80% not to 80%
Statistics only come to play to figure out our new chances.

In game design, it has to be stated whether it’s multiplicative or additive. Sometimes a logarithmic function is used as well, with increases in efficiency as 1 / ( 1 + bonus ). This allows you to always add more bonus, but there’s diminishing returns.

I play video games; I need to know if the percentage is additive or multiplicative.

"+100%" looks pretty good until you see what "×25%" actually gives you.

When my son was about to be born my mother in law caught wind that we didn't plan on circumcising (before researching it I mostly felt it was just strange to do cosmetic surgery on a newborn) but her argument was mostly parroting the 50% reduction in this that and the other disease, missing the fact that it was going from a 0.5% chance to a 0.25% chance, but of course introduced new risks by nature of being a surgery.

Naturally after looking more into it I learned just how bonkers circumcision is so I was far more cemented in my position

Funny thing is this is a language issue, not a math issue.

It's really pretty simple - if something increases by 80%, you add 80% of whatever it already is... one dollar becomes $1.80... one percent becomes 1.8 percent.

Most people don't understand it because they've seen it done wrong so often, the wrong way seems right.

I work in a place full of statisticians, and we've had to unfortunately have numerous conversations with some of them about the difference between "a decrease" and "a decrease in the rate." Apparently "it's increasing slower" isn't clear enough for some.

I've always wondered how to disambiguate multiplication and addition of percentages. I guess that's what percentage points are for?

Difference between increase of x% (old percentage + old percentage * x%)% and increase of x percentage points (old percentage and x)%

well it's ambiguous. Its also a sloppy way of expressing an increase by 80 percentage points.

So you're telling me there's a chance?

Wrong: I had a 1% chance, and I doubled my chances. Now my chances are 101%.

Right: I had a 1% chance, and I doubled my chances. Now my chances are 2%.

Wrighongt: I had a 1% chance, and I doubled my chances. Now my chances are 3%, because I'm a lucky person.

People got this wrong about inflation as well. In 2020 there was actual deflation, and in 2021 there was very minimal inflation, meaning prices were still largely lower or similar as 2019. Then we saw 9% inflation in 2022. Total inflation in 2024 vs the 2019 benchmark was around 15%. Or 3% average per year, which is barely over the baseline. People just hear 9% inflation, completely missing the fact that this was a YoY number relative to the Trump recession.

That's why when presenting numbers at work, we always distinguish a movement of X % (percent) from a movement of X ppts (percentage points)

Dark Souls cleared this up for me real quick.

I know all this. I play DPS!