Which type of Control Chart should be used to monitor the percent defective parts in a sample?

The utilization of an Attribute Control Chart is appropriate for monitoring the percent defective parts in a sample because this type of control chart is designed specifically for quality characteristics that can be counted and classified into discrete categories. In quality control, attributes represent non-measurable characteristics, such as pass/fail, defective/non-defective, or the presence/absence of a feature.

Since you are focused on the percent defective, you are dealing with a situation where you are observing the count of defective items within a fixed sample size. An Attribute Control Chart is set up to track the proportion of defectives in this manner. By plotting these proportions over time, it allows teams to visually assess stability in their process and determine whether there are any shifts or trends that may indicate a need for corrective action.

In contrast, a Variables Control Chart is used for continuous data that can be measured on a scale, such as weight, length, or temperature. Since you're focusing on a categorical assessment (defective vs. not defective), the variables method is not suitable here. Thus, the Attribute Control Chart serves the purpose of monitoring defect rates effectively.