A manufacturing plant is experiencing a high defect rate (15%) in its automated welding process for car frames. Apply the Six Sigma DMAIC methodology to address this issue.

A bottling plant fills 500ml water bottles. The target volume is exactly 500ml. A control chart tracking the fill volume shows most points clustered around 500ml, but suddenly, the last five data points are all steadily decreasing (498ml, 496ml, 493ml, 490ml, 485ml). Classify the type of variation and explain the necessary action.

An engineering firm implements Six Sigma quality standards for a critical aerospace component. What exactly does it mean to achieve a "Six Sigma" level of quality regarding defect rates?