If you include the fact that you never bought it, that's more information that affects the probabilities. It's just like in the Monty Hall problem where revealing a goat behind one door changes the probabilities of what's behind the other doors.
Given the fact that cannabis was recently made legal where you live, you may be 5% less like to pass a class. Given the additional fact that you chose not to use cannabis, you may be 5% more likely to pass a class due to the curve being lowered by those who do smoke.
I thought we already knew the academic impact of canibus use from the documentary Fast Times at Ridgemont High
I thought the characters drove their cars to school in that movie.
Our small software company had a customer that would often complain, "The computer is sticking it's tongue out at me again!" For a custom module, I installed an error dialog for one particular error that displayed an animated face sticking it's tongue out. When she finally ran into this error, she was so tongue tied, she for the first time did *not* say "The computer is sticking it's tongue out at me!"
Lots of folks confuse bad management with destiny. -- Frank Hubbard