Pareto Diagram helps teams focus on the small number of really important problems or causes of problems. This tool is useful in establishing priorities by showing which are the most critical problems to be tackled or causes to be addressed. Comparing Pareto diagram of a given situation over time can also determine whether an implemented solution reduced the relative frequency or cost of that problem or cause.
The chart is similar to the histogram or bar chart, except that the bars are arranged in decreasing order from left to right along the abscissa. Each bar represents only a category of faults, arranged in a decreasing way, from left to the right, according to their importance.The steps necessary to construct a Pareto diagram are:-
Step 1 - Record the raw data. List each
category and its associated data count.
Step 2 - Order the data. Prepare an analysis
sheet, putting the categories in order and placing the one with the largest
count first.
Step 3 - Label the left-hand vertical axis.
Make sure the labels are spaced in equal intervals from 0 to a round number
equal to or just larger than the total of all counts. Provide a caption to
describe the unit of measurement being used.
Step 4 - Label the horizontal axis. Make the
widths of all of the bars the same and label the categories from largest to
smallest. An "other" category can be used last to capture several
smaller sets of data. Provide a caption to describe them. If the contributor
names are long, label the axis A, B, C, etc. and provide a key.
Step 5 - Plot a bar for each category. The
height of each bar should equal the count for that category. The widths of the
bars should be identical.
Step 6 - Find the cumulative counts. Each
category's cumulative count is the count for that category added to the counts
for all larger categories.
Step 7 - Add a cumulative line. This is
optional. Label the right axis from 0 to 100%, and line up the 100% with the
grand total on the left axis. For each category, put a dot as high as the
cumulative total and in line with the right edge of that category's bar.
Connect all the dots with straight lines.
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