Fixed Ratio: Factory workers are paid 100$ each for every 5 tires that are made.
Variable Ratio: In a slot machine, the player has no idea on what spin that he'll win $500 dollars.
Fixed Interval: Everyday at about 6:00, a child eats dinner. Soon enough after 6:00, a child keeps on getting hungry.
Variable Interval: Everyday at 12:30, a worker gets his 1 hour lunch break.