One of the Total Quality Management Tools is the Histogram.
One uses this graph to show frequency distributions. It looks very much like a bar chart.
When to Use:
This chart graphs data distrubutions. If you have numerical, variablle, continuous data you can use the this chart. The chart organizes and sorts the data. It shows the data in a pictorial format.
Collect at least 50 data points from a process.
Use the worksheet below to set up the chart. It helps you determine the number of bars, the width of the bar, and the labels for the bar edges.
After calculating width in step 2 of the worksheet, use your judgment and adjust it to a convenient round number. For example, you might decide to round 0.9 to an even 1.0. The value for W may not have more decimal places than any number in your data set.
Draw x- and y-axes on graph paper. Mark and label the y-axis for counting the data values. Mark and label the x-axis with the L values from the worksheet. The spaces between these numbers will create the bars. Do not allow for spaces between bars.
For each data point, locate it where it fits within the Ls. Mark off one count above the appropriate bar with an X or by shading that portion of the bar.
Consider this simple example. Below shows the exam results collected from a training class of 50 individuals:
Below is the chart. The center of the data shows about 69. The average is probably near 69. Construct these bar charts to provide
a useful picture of your data.
To see many examples of histogram and learn more details, see this page