The Funnel Experiment

The Funnel Experiment was devised by Dr. Deming to describe the adverse effects of tampering with a process by making changes to it without first making a careful study of the possible causes of the variation in that process.


In the experiment, a marble is dropped through a funnel onto a sheet of paper, which contains a target. The objective of the process is to get the marble to come to a stop as close to the target as possible. The experiment uses several methods to attempt to manipulate the funnel’s location to achieve the objective.

The learning or “rules” of the experiment can be applied to many different types of tampering and common kneejerk reactions on the part of management, all of which are impediments to effective management and continual improvement, including:

  • Adjusting a process when a part is out of specifications
  • Making changes without the aid of control charts
  • Changing company policy based on the latest attitude survey
  • Modifying the quota to reflect current output
  • Using variances to set budgets
  • Relying on history passed down from generation to generation