Table of Contents

* This study guide was updated on 29 Aug, 2009.

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SAMPLE TEXT on C Chart, P Chart and U Chart

A C chart is a data analysis technique you may use for determining if a measurement process has gone out of statistical control. It is quite sensitive to changes in the number of defective items in the measurement process. The “C” asually stands for “counts” as in defectives per lot. There are two axises: the vertical axis is the number defective for each sub-group, while the horizontal axis is the sub-group designation. Note that the C chart would assume that each sub-group has an equal sample size , and that a sub-group is typically a time sequence, such as the number of defectives in a production run.

The U Chart is similar to the C chart. The distinction is that the latter is mostly used when the material being measured is constant in area and the sub-groups have equal size. On the other hand, the former would be used when those assumptions cannot be met.

The P chart is also similar to the C chart. It is highly sensitive to changes in the proportion of defective items in the measurement process. The “P” in fact stands for the proportion of successes of a binomial distribution. A typical P control chart would have a Vertical axis (representing the percentage of defectives for each sub-group) and a Horizontal axis (which is the sub-group designation).
 

SAMPLE TEXT on Lean Six Sigma

Lean can't really bring a process under statistical control. On the other hand, Six Sigma alone can hardly improve process speed or reduce invested capital in a sufficient manner. However, both of them can enable the reduction of the cost of complexity. Combining them together is therefore not a bad idea.

Six Sigma stresses the need to recognize opportunities and eliminate defects as defined by customers. It recognizes that variation hinders our ability to reliably deliver high quality services. It requires data driven decisions. It incorporates quality tools under a powerful framework for effective problem solving. It also provides a highly prescriptive cultural infrastructure effective in obtaining sustainable results.

Lean focuses on maximizing process velocity, by providing tools for analyzing process flow and delay times at each activity in a process, and by centering on the separation of "value-added" from "non-value-added" work with tools to eliminate the root causes of non-valued activities and their cost. It is believed that Lean implementation such as that in manufacturing would always require a complete change of traditional management and thinking patterns. Concepts of lean would always be based on flow of value and identification and removal of waste.

Value is always defined from a customer’s perspective. A value stream can have two forms, the first an internal sequence of activities that must be combined and the second concerns the business, its customers and its suppliers along the supply chain. The internal value stream includes all the assets, people and processes to manufacture products. The supply chain value stream covers every organization that must combine to produce the final product offered.