The Seven Tools of Quality

As most quality assurance professionals can attest, superior quality control hinges on the singular idea of measurement. Accurate measurements are of course dependent upon several factors, but none more so than the instruments used in the execution of the process. Over time, and as quality control and assurance has become its own full-fledged industry, a set of basic quantitative tools has emerged as the most commonly used means of achieving the desired level of quality. These tools are commonly referred to as ''The Seven Tools of Quality'' and consist of the following:

Ishikawa Diagram — also known as the fishbone diagram or the cause-and-effect diagram, the Ishikawa diagram was developed and implemented by Kaoru Ishikawa, a professor at the University of Tokyo. The main purpose of this diagram is to identify the cause(s) of a particular event. Causes are identified in the diagram according to three different categories: the 6 M’s (machine, materials, man, method, measurement, and mother nature), the 8 P’s (people, place/plant, policies, price, promotion, processes, procedures, and product), and the 4 S’s (skills, surroundings, suppliers, and systems).

Pareto Chart — this is a specific type of bar chart in which values are plotted in descending order. This type of graph also usually includes a line graph displaying the cumulative totals of involved categories. It is named after Vilfredo Pareto, a French-Italian economist who was a pioneer in the field of microeconomics.



Check Sheet — this is a straightforward document used to collect data while it is being produced. This tool is the most simple and easy to read of the seven tools of quality and appears in five basic types: classification, location, frequency, measurement scale, and check list.

Control Chart — this chart is used to determine whether or not statistical control (or monitoring) exists within a manufacturing or business process. This is an important tool in understanding how reliable a process or application is and whether its future performance can be reasonably predicted. If mistakes or variations occur within the process, the control chart can help identify where, when, and how they are occurring.

Flowchart — this diagram depicts the flow and interaction of elements of a system in a business process. The flowchart is commonly used by businesses or manufacturers to identify flaws or the source of common and widespread problems within the system.

Histogram — another type of graph which measures frequencies. Companies often divide their output into different categories and must have reliable data showing which categories are the most likely to occur and whether or not this is good for the bottom line. For example, if a farmer plants six groves of trees and finds that the medium-sized trees produce the most fruit, he or she will likely aim to plant trees of similar size.

Scatter Diagram — this diagram depicts values for two variables from a single set of data. The values are identified simply as points which together appear as a cluster of dots across the graph and can help determine median or mean values of the parameters and variables being used.