About the cheese-bed entanglement correlation, it could be that wealthier populations eat more cheese; wealthier populations also live longer, and the elderly are more likely to get seriously hurt and die by becoming entangled in their bedsheets. So it could be hypothesis 3: C causes A and B.

Loving the Harry Potter examples!

Gryffindor ----> bravery

Snape exhibits bravery.

"Snape is a Gryffindor" is confusing sufficiency for necessity.

It should be "most students in Professor Slughorn's class can brew potions masterfully . . ." The Slug Club is Professor Slughorn's club and only exists when he is the potions professor at Hogwarts.