About the exercise, calulcating the difference
Why in the video we calculate Before-After, but in the exercise we calculate After-Before? I don't understand why we don't calculate the weight before minus the weight after
I think in the exercise, they wanted to be as much as precise. i.e. "you lost -x weight" like getting minus value from your weight is losing weight.
Anyway, you would do it the other way (before - after) you will get the same result as this one-sided testing.
Hope this explains.
I also had hard time to consume these concepts, I did my extra research on youtube etc. and I was able to understand a bit more.