For example, temperature data rounded off to the nearest 0.2 degree would show a comb shape if the bar width for the histogram were 0.1 degree.

A histogram is the most commonly used graph to show frequency distributions.

It looks very much like a bar chart, but there are important differences between them.

This helpful data collection and analysis tool is considered one of the seven basic quality tools.

After calculating W 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.

Mark and label the x-axis with the L values from the worksheet.

The spaces between these numbers will be the bars of the histogram.

If any unusual events affected the process during the time period of the histogram, your analysis of the histogram shape likely cannot be generalized to all time periods.

Typical histogram shapes and what they mean are covered below.

In a normal or typical distribution, points are as likely to occur on one side of the average as on the other.

Statistical calculations must be used to prove a normal distribution.

For example, many processes have a natural limit on one side and will produce skewed distributions.

This is normalmeaning typicalfor those processes, even if the distribution isnt considered normal.

The distributions peak is off center toward the limit and a tail stretches away from it.

For example, a distribution of analyses of a very pure product would be skewed, because the product cannot be more than 100 percent pure.

Other examples of natural limits are holes that cannot be smaller than the diameter of the drill bit or call-handling times that cannot be less than zero.

These distributions are called right- or left-skewed according to the direction of the tail.

The outcomes of two processes with different distributions are combined in one set of data.

For example, a distribution of production data from a two-shift operation might be bimodal, if each shift produces a different distribution of results.

Because there are many peaks close together, the top of the distribution resembles a plateau.

Usually this is caused by faulty construction of the histogram, with data lumped together into a group labeled greater than.

This distribution often results from rounded-off data andor an incorrectly constructed histogram.

Histogram Excel 16 For Mac