Every alternate day, quality control inspectors at McHeinz Inc. randomly select items from an assembly line for inspection, and compliment the workers for every product that meets their expectations on quality. However, they vary the number of items they inspect each time. This motivates the employees to put in more effort to ensure that all the items are of the required quality. What reinforcement schedule are the quality control inspectors using?

Variable-ratio

Explanation:

Variable-ratio schedule: In psychology, the term "variable-ratio schedule" is described as one of the different reinforcement schedules in the operant conditioning theory which was proposed by B. F. Skinner. In the variable-ratio schedule, a specific response is being reinforced after an "unpredictable or unforeseeable number" of responses. However, the variable-ratio schedule creates a steady yet high rate in terms of response.

Example: Gambling.

In the question above, the given statement represents a variable-ratio schedule.