Six Sigma Green Belt Certification Practice Exam

Your manufacturing process uses a special part delivered from three separate manufacturing plants. Which sampling technique would you use to test the part?

1. Stratified sampling

2. Multiple sampling

3. Sequential sampling

4. Random sampling

The correct answer is: Stratified sampling

The correct choice of stratified sampling is ideal in this scenario because it allows for the representation of different subgroups within the overall population—in this case, the parts delivered from the three separate manufacturing plants. By using stratified sampling, you can ensure that each plant is represented in the sample according to its proportion of the total deliveries. This is particularly important when you suspect that there might be differences in quality or characteristics of parts produced by each plant. Stratifying the sample helps in capturing variations that could affect the manufacturing process or final product quality, leading to more accurate and reliable test results. When analyzing the data, you can also identify if one plant is contributing more defects than others, which enables targeted improvements. In contrast, while the other sampling methods can provide useful insights, they do not guarantee a representation based on the specific groups present. Multiple sampling focuses on making several samples and would not represent differences among the plants specifically. Sequential sampling minimizes the number of samples needed to reach a conclusion but does not account for variability among the plants. Random sampling may introduce bias if the parts from each plant are not equally likely to be selected, potentially overlooking quality issues tied to a specific plant. Hence, stratified sampling is the most effective choice for this scenario