Monday, November 29, 2010

The Magnificent Seven

In the pursuit of quality, it is necessary to utilize techniques to analyze and evaluate metrics in a quality-oriented fashion. There are seven basic techniques that have been utilized for many decades now in the world of quality management. The utilization of these techniques has resulted in organizations making great strides in their quality management efficiency and quality delivered to the customer.

The seven techniques are as follows:

  • Cause and Effect Diagram (Ishikawa Diagram): This breaks down the possible cause of a variation from specifications into six different areas – People, Methods, Machines, Materials, Measurements and Environment. These can be further subdivided into smaller components. The basic idea is to link these areas to the process in order to evaluate which area (or sub-area) could be causing problems. This can be used proactively to evaluate the process for problems before they happen or reactively to zero in on a problem once it has manifested itself.

  • Check Sheet: This is a simple document that is used for collecting data in real-time and at the location where the data is generated. The document is typically a blank form that is designed for the quick, easy, and efficient recording of the desired information, which can be either quantitative or qualitative. When the information is quantitative, the check sheet is sometimes called a tally sheet. There are 5 basic types of check sheets: Classification, Location, Frequency, Measurement Scale and Check List.

  • Control Charts: A control chart consists of points representing a statistic with
  • mean, standard deviation and upper and lower control limits also displayed. If analysis of the control chart indicates that the process is currently under control then data from the process can be used to predict the future performance of the process. If the chart indicates that the process being monitored is not in control, analysis of the chart can help determine the sources of variation, which can then be eliminated to bring the process back into control.

  • Histogram: A histogram consists of tabular frequencies, shown as adjacent rectangles, erected over discrete intervals (bins), with an area equal to the frequency of the observations in the interval. Histograms are used to plot density of data, and often for density estimation: estimating the probability density function of the underlying variable. The histogram provides insight on the problem (or potential problem) that may be related to the data being plotted.

  • Pareto Chart: A Pareto chart contains both bars and a line graph, where individual values are represented in descending order by bars, and the cumulative total is represented by the line. The purpose of the Pareto chart is to highlight the most important among a (typically large) set of factors. In quality control, it often represents the most common sources of defects, the highest occurring type of defect, or the most frequent reasons for customer complaints, and so on.

  • Scatter Diagram: A scatter diagram uses Cartesian co-ordinates to display values for two variables for a set of data. A scatter plot can suggest various kinds of correlations between variables with a certain confidence interval. Correlations may be positive (rising), negative (falling), or null (uncorrelated). If the pattern of dots slopes from lower left to upper right, it suggests a positive correlation between the variables being studied. If the pattern of dots slopes from upper left to lower right, it suggests a negative correlation. A line of best fit (alternatively called 'trend line') can be drawn in order to study the correlation between the variables.

  • Stratification: Stratification is a technique that separates data gathered from a variety of sources so that patterns can be observed. These patterns can then be further analyzed to zero in on the root cause of the problem.

The seven basic techniques of quality management have been staples in the toolbox of any quality professional for a long time now. It does not take a lot of effort to start utilizing these techniques in your organization quickly and efficiently. There is really no reason why any and every company shouldn’t be using these tools extensively.

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