Final answer:
A p-chart is the preferred method for controlling the quality issue of defective airline seat audio systems. It is designed for attribute data, such as the defective or non-defective status of an item, which applies to this scenario.
Step-by-step explanation:
To address the issue of passengers seated at seats with a defective audio system, the preferred type of control method focuses on the proportion of defects in the sample of items. In quality control terminology, when the data consists of attributes (pass/fail, defective/non-defective), a p-chart is the most appropriate tool to use, as it tracks the proportion of defective units in a process.
The p-chart is designed for use with a binary variable, typically labeled defective or non-defective, which makes it ideal for tracking the incidence of specific issues like the audio system defect in an airline's seats. An x-bar chart or R-chart is more suitable for variable data where the quality characteristic is measured on a continuous scale. Meanwhile, Cpk is a measure of the capability of a process, considering both the process variability and the process mean, but it's commonly used with continuous data rather than attribute data.
Therefore, a p-chart is the best control method among the given options for tracking and controlling the quality of airline seats' audio systems.