Analyze the following design. Is this a sample survey, an observational study or an experiment? What are the populations, the parameters of interest and the sample procedure. If an observational study, was it retrospective or prospective? If an experiment, describe the factors, treatments and any blocking, matching or blinding.

A soft drink company must be sure the bottle caps on the soda are fully sealed and will not come off easily. Inspectors pull a few bottles off the production lines of regular intervals and test the cap. If they detect any problem, they will stop the bottling process to adjust or repair the machine that caps the bottles.