Which measurement estimates the percentage of the population that meets specifications?

The Ppk measurement is designed to estimate the percentage of the population that meets specifications by considering both the process variability and the process mean. Specifically, Ppk factors in the actual performance of an individual process against the specifications set for the product or service being evaluated. It takes into account how centered the process is relative to the target, as well as how much the process varies.

When calculating Ppk, it's important to note that it uses the actual process data, which allows for a more accurate reflection of real-world performance. This means it provides insights into how many units produced fall within the acceptable limits established by specifications, giving a clear quantitative picture of process capability in relation to meeting customer requirements.

By contrast, other measurements like Cp, CpK, and Pp also assess process capability but may not fully encapsulate the performance against specifications in the same way as Ppk. Cp and Pp do not account for the process mean relative to the target, while CpK considers the mean but does not reflect actual process data as precisely as Ppk does. Thus, Ppk is the most suitable measurement for estimating the percentage of the population that meets specifications effectively.