Statistics Applied to Quality Control

Statistics Applied to Quality Control

1. 1950´s Deming went to Japan and trained hundred of Japanese engineers,managers and scholars in statistical process control.

   • One of the members was Kaoru Ishikawa, profesor at the University of Tokyo
     • He wanted to "democratize quality",to make quality control comprehensible to all workers
       • Inspired by Deming´s lectures he formalized the:
         • Seven Basic Tools of Quality
           • Cause and Effect Diagrams
             • Also known as Ishikawa and Fishbone Diagrams, employed to identify the root cause.
               • The method forces the user to consider all the likely causes of a problema,not the obvious ones.
                 • Combining :brainstorming and graphical analysis
           • Pareto Charts
             • Named after Vilfredo Pareto. Is a type of chart that contains both barts and a line graph.
               • The purpose of Pareto Chart is to highlight the most important among a (typically large) set of factors
               • Individual values are represented in descending order by bars and the cumulative total is represented by the line.
           • Control Charts
             • Also known as shewhart charts or process behaviour charts,are tools used to determine whether or not a manufacturing or business process is in a state of statistical control
               • If the chart indicates that the process is under control,the data can be used to predict the future performance of the process
               • If the chart indicates that the process is not in control, the analysis of the chart can help determine the sources of variation and eliminated to birng process back into control
           • Check Sheet
             • Is a simple document used for collecting data in real time and at the location where the data is generated.
               • A characteristic of it, is that the data is recorded by making marks on it, is divided into regions and have different regions
                 • Regions:Classification,location,frequency,measurement scale and check list
             • Is typically a blank form designed for the quick,easy and efficient recording of the info
           • Scatter Plots
             • Is a type of mathematical diagram using Cartesian coordinates to display values for two variables for a set of data
               • The data is displayed as a collection of points,is used when a variable exists that is under the control of the experimenter
               • One of the most powerful aspects of a scatter plot is its ability to show nonliner relationships between variables.
           • Flow Chart /Histogram
             • Is a graphical representation, show a visual impression of the distribution of data
             • Introduced by Karl Pearson,consist of tabular frequencies.
             • Are used to plot density of data and often for density estimation.
           • Deming Cycle
             • Was made popular by Dr W Edwards Deming,father of the modern quality control
               • Plan, Do, Study and Act, must help to change the demand for goods by showing how to close up the tolerance range and to improve the quality of goods
                 • Iteration is the fundamental principle
                 • Ishikawa has expanded Deming´s four step into six.
                   • Plan :Determine Goals and targets,determine methods of reaching goals
                   • Do: Engage in education and training,Implement work
                   • Check: the effects of implementation
                   • Act: take appropriate action