Description:

One of Total Quality Management Tool is Histogram.

it is the most commonly used graph to show frequency distributions. It looks very much like a bar chart.

When to Use:

When the data are numerical, and you want to see it in graph , so it will by more easy to understand the data .

Construction :

• Collect at least 50 consecutive data points from a process.

• Use the worksheet below to set up the histogram. It will help you determine the number of bars, the range of numbers that go into each bar and the labels for the bar edges.

After calculating Width in step 2 of the worksheet, use your judgment to adjust it to a convenient number.

For example, you might decide to round 0.9 to an even 1.0. The value for W must not have more decimal places than the numbers you will be graphing.

• Draw x- and y-axes on graph paper. Mark and label the y-axis for counting data values. Mark and label the x-axis with the L values from the worksheet. The spaces between these numbers will be the bars of it. Do not allow for spaces between bars.

• For each data point, mark off one count above the appropriate bar with an X or by shading that portion of the bar.

Example

There are 50 measurements, But it is difficult to draw specific conclusionsabout the data without further analysis…. Right ? . Histograms can be constructed to provide more usable information as below.