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A paper and pencil approach to improving the reliability and consistency of your products and services.

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Dot Plots

Use Dot Plots to collect numerical or rank data, and to get a quick look at how it is distributed. Be careful not to use Dot Plots with data that have already shown a time-based bias. The reason for this is that the sampling interval may greatly effect the numbers you draw, giving you a false impression of what is going on. Dot Plots are best used when the full range of possibilities are expressed along the horizontal axis, and there are many repeated values. Note, Dot Plots can only be used to collect data as whole integers. Values that are fractions, (with decimal points) can complicate data collection efforts significantly.


	The above Dot Plot was created and used by a telephone order taker to record how many items customers were ordering. You can tell just by looking at it that roughly half the orders consisted of nine or fewer items, and the other half included ten or more items. This also means that the average order was between nine and ten items. This information can provide the company with guidance as to the ideal size of box in which to package orders, and it also provides important clues as to the buying habits of customers. Notice that the dots are spaced evenly, allowing us to get a look at the shape of the distribution.

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The eManual of Quality Improvement - Synerlux Consulting, 2005. All Rights Reserved.

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