The following scenario can happen, and is actually very close to reality:
1) Being vaccinated increases your chance of being infected by covid by16%
2) If you are 60 or older than 60 years, being vaccinated halves your chance of being infected by covid.
3) If you are younger than 60 years, being vaccinated halves your chance of being infected by covid.


In other words, being vaccinated increases your chance of infection, while getting vaccinated decreases your chance of infection.

Edited 12/1/2021 00:31:11

lol

This is just Simpson's Paradox. Another one example (politics warning) is that Democrats had higher opposition to the 1960s Civil Rights bills but this was due to Democrats having more Southern members. Northern Democrats supported Civil Rights more than Northern Republicans and Southern Democrats likewise supported Civil Rights more than Southern Republicans.

Similarly, I'd wager that the 60+ crowd is overrepresented among the vaccinated so P(infected|vaccinated) is higher because P(infected|old) and P(old|vaccinated) are high.

I would wager that 13% of the population commits half of the crime

Only about 1 in 600 Americans commit violent crime in a given year. 0.2% are responsible for 100%, no need to blame 12.9% for the behavior of 0.1%.

@l4v.r0v

Violet crimes or non-violet,

We all desire a safe, rich neighbourhood with NO crime,

ain't that right?

https://www.youtube.com/watch?v=hNDgcjVGHIw

It is not just a Simpson's Paradox.
It is very rare for a mathematical paradox to go so viral as this went. Alas, nobody (at least in my country) explained the beautiful paradox more closely.

Edited 12/1/2021 11:32:35

Scenario: Two runners compete against each other in a 100 meter sprint.

Facts:

Runner #1 (Bob) crosses the finish line with a time of 11.45 seconds.
Runner #2 (Steve) crosses the finish line with a time of 11.53 seconds.

Spin:

Fox News: Steve finished the race less then 0.1 seconds behind the winner!
CNN: Steve lost the race. He came in dead last. The last person to cross the finish line.