Statistical Quality Control Essay Example

problems is not enough. We need specific tools that can help us make the right quality decisions. These tools come from the area of statistics and are used to help identify quality problems in the production process as well as in the product itself. Statistical quality control is the subject of this chapter.

Statistical quality control (SQC) is the term used to describe the set of statistical tools used by quality professionals. Statistical quality control can be divided into three broad categories: 1 . Descriptive statistics are used to describe quality characteristics and relationships.

Included are statistics such as the mean, standard deviation, the range, nd a measure of the distribution of data. Marketing, Management, Engineering Statistical quality control (SQC) The general category of statistical tools used to evaluate organizational quality. Descriptive statistics Statistics used to describe quality characteristics and relationships.

173 2. Statistical process control (SPC) involves inspecting a random sample of the output from a process and deciding whether the process is producing products with characteristics that fall within a predetermined range.

SPC answers the question of whether the process is functioning properly or not. .

Acceptance sampling is the process of randomly inspecting a sample of goods and deciding whether to accept the entire lot based on the results. Acceptance sampling determines whether a batch of goods should be accepted or rejected. The tools in each of these categories provide different types of information for use in analyzing quality. Descriptive statistics are used to describe certain quality characteristics, such as the central tendency and variability of observed data.

Although descriptions of certain characteristics are helpful, they are not enough to help us evaluate

whether there is a problem with quality.

Acceptance sampling can help us do this. Acceptance sampling helps us decide whether desirable quality has been achieved for a batch of products, and whether to accept or reject the items produced. Although this information is helpful in making the quality acceptance decision after the product has been produced, it does not help us identify and catch a quality problem during the production process. For this we need tools in the statistical process control (SPC) category.

All three of these statistical quality control categories are helpful in measuring and evaluating the quality of products or services.

However, statistical process control (SPC) tools are used most frequently because they identify quality problems during the production process. For this reason, we will devote most of the chapter to this category of tools. The quality control tools we will be learning about do not only measure the value of a quality characteristic. They also help us identify a change or variation in some quality characteristic of the product or process.

We will first see what types of variation we can observe when measuring quality. Then we will be able to identify specific tools used for measuring this variation. Variation in the production process leads to quality defects and lack of product consistency. The Intel Corporation, the world's largest and most profitable manufacturer of microprocessors, understands this. Therefore, Intel has implemented a program it calls "copy-exactly' at all its manufacturing facilities.

The idea is that regardless of whether the chips are made in Arizona, New Mexico, Ireland, or any of its other plants, they are made in exactly the same way.

This

means using the same equipment, the same exact materials, and workers performing the same tasks in the exact same order. The level of detail to which the "copy-exactly' concept goes is meticulous. For example, when a chipmaking machine was found to be a few feet longer at one facility than another, Intel made them match. When water quality was found to be different at one facility, Intel instituted a purification system to eliminate any differences.

Even when a worker was found polishing equipment in one direction, he was asked to do it in the approved circular pattern.