Six Sigma Green Belt Certification Practice Exam

Which control chart is suitable for analyzing attribute data?

1. np chart

2. X-bar - R chart

3. MX-bar - MR chart

4. Median chart

The correct answer is: np chart

The np chart is specifically designed for analyzing attribute data, which involves measurements that are categorized into distinct groups, typically indicating whether an item meets a specified criterion (like pass/fail, defective/non-defective). An np chart displays the number of defective items in a fixed sample size, making it an effective tool for monitoring the proportion of defective items over time. In the context of Six Sigma and quality control, attribute data is often used when quality characterizations are binary. This uniquely positions np charts for applications where decisions are based on counts of successes or failures. The np chart helps in identifying trends, shifts, or changes in the process that could signal a need for intervention in order to maintain quality. On the other hand, the X-bar - R chart and the MX-bar - MR chart are designed for variable data, which involves measurements on a continuous scale. These charts track means and ranges of measurements, which do not apply to data categorized as attributes. Similarly, the Median chart is also suitable for variable data analysis. Therefore, the np chart stands out as the appropriate choice for situations involving attribute data.