I used this set:

x,y
1,2
2,2
3,3
4,3
5,3.8
6,4.2
7,4

On my (emulated) TI-84 Plus, I got this result: https://photos.app.goo.gl/vmQ47RBT8p6tqNaG6

And on a separate statistics program (https://github.com/Benny121221/wstat) I got this printout:

However, using ScottPlot, I got the same offset, but the slope was 0.3200000. The proper slope is 0.4

I cannot see anything in the code that is obviously incorrect, however it is strange to me that the linreg code cares about the x-spacing, the spacing of x values doesn't matter to the LSRL.

I will make a PR to try and fix this, hopefully without causing any breaking changes.