Schedules of Reinforcement
An example of a fixed-ratio schedule would be, you have 3 tests on September 30th that you need to study for, and if you get 90% or higher on those tests, you get a sticker.
An example of a fixed-interval schedule would be, you get to work on time for a straight two weeks and get a bonus on your paycheck.
An example of a variable-ratio schedule would be, you are in a casino playing blackjack and if you win you get money.
An example of a variable-interval schedule would be, you are cooking chicken in the oven and the box says to cook the chicken for 20-22 minutes.