How can you tell the difference between an interval and a ratio schedule of partial reinforcement?

There are 4 subcategories for partial reinforcement schedules: ratio, interval, fixed, and variable. If the schedule is developed based on the frequency of a behavior, it is a called a ratio schedule. If a schedule is developed based on the amount of time that has elapsed, it is called an interval schedule.

Interval means the schedule is based on the time between reinforcements, and ratio means the schedule is based on the number of responses between reinforcements. Reinforcement is delivered at predictable time intervals (e.g., after 5, 10, 15, and 20 minutes).