From the course: Six Sigma: Green Belt
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Graphical displays of variation
- Let's say you have two suppliers, A and B. They're supposed to deliver a product within 24 hours. They both report the same average delivery time of 23 hours. Are they performing well? And why are some customers still complaining about late deliveries? To answer these questions, we have to go beyond just the average delivery times. We have to plot the data to see the variability of variation in delivery times. We need graphs that display variation. For continuous data, graphs and charts commonly used are dotplots, histograms, and boxplots. These graphs display how spread out the data points are, in addition to where they are centered. Here, we have a dotplot for delivery times of suppliers A and B. Each dot represents a data point. And the horizontal axis is the timescale in hours. While both have the same mean of 23 hours, there is a lot more variation in A, with many deliveries exceeding 24 hours. I prefer B to be…
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