Analyzes observed differences in the process proportion defective at two settings of an input. Use the 2-proportions test when the data from the process are discrete and have exactly two levels (for example, pass or fail) and the factor being evaluated has exactly two levels (for example, fast or slow, before or after). You must collect a sample at each level of the input variable.
|When to Use||Purpose|
|Mid-project||Fixing an input at two different settings (levels) helps to determine which inputs have significant influence on the proportion defective of the output.|
|End of project||Verify a significant reduction in the process proportion defective results from the implemented improvements. Of course, this step assumes one of the goals of the project was to reduce the proportion defective.|
Discrete Y at two levels (for example, good or bad), a single X at two levels.