Of course there's always a relevant XKCD

Love it

It took too long for me to realize it was the same data.

If you're in a college statistics course and you're doing graphs by hand and not generated entirely be statistics software, the skills you're learning are useless anyway.

Yeah that would be bad practice, industry standard is to run all the tests simultaneously and if something comes out statistically significant make up a narrative then try to split it into 4 papers.

Folks in observation and analytics are gonna be real mad when they realize you're giving away their secrets.

Could be valid. Now if it had been logarithmic the pro tip might still be true, since many don't look at the axis either.

My guess is lower. I'd put the correlation at about -.35 to -.45, so that'd correspond to an R² of .1225 to .2025. But eyeballing correlations is hard.

Assuming it's a correction line, I don't think you can tell from the slope of that line alone as the clustering will matter and correlations are finicky. Now, if it was a regression coefficient, that sexy line can be calculated just by looking at it (although we'd want to know if it was significant, lol).

Delete enough data points and it will be 1. You'll only have two data points, but you'll have bragging rights.