Basic quality tools

Basic quality tools

1. Cause and effect Diagram

   • Ishikawa diagram
     • Kaoru Ishikawa
   • Uses
     • When identifying possible causes for a problem
     • Especially when a team’s thinking tends to fall into ruts.
   • Causes
     • Methods
     • Machines (equipment)
     • People (manpower)
     • Materials
     • Measurement
     • Environment

2. Check Sheet

   • useful in Lean Six Sigma projects
     • Charactheristics
       • tabular check sheets or tally sheets
   • When to use the check sheet
     • the data can be observed and collected repeatedly
       • by either the same person or the same location
   • simple and effective way to display data

3. Control Chart

   • improvement projects
     • begins with a time series graph.
       • central line (X) is added as a visual reference for detecting shifts or trends – this is also referred to as the process location.
         • Upper and lower control limits (UCL and LCL) are computed from available data and placed equidistant from the central line. This is also referred to as process dispersion.

4. Histogram

   • Karl Pearson
   • kind of bar graph
     • the first step is to "bin" the range of values
       • the next step is to make a table of frequencies
         • then, Drawing the Histogram
           • 1 Draw a horizontal line. This will be where we denote our classes.
           • 2. Place evenly spaced marks along this line that correspond to the classes.
           • 3. Label the marks so that the scale is clear and give a name to the horizontal axis.
           • 4. Draw a vertical line just to the left of the lowest class.
           • 5. Choose a scale for the vertical axis that will accommodate the class with the highest frequency.
           • 6. Label the marks so that the scale is clear and give a name to the vertical axis.
           • 7. Construct bars for each class. The height of each bar should correspond to the frequency of the class at the base of the bar. We can also use relative frequencies for the heights of our bars.

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