Page 260 - Lean six sigma demystified

238 Lean Six Sigma DemystifieD

These two outcomes can be easily monitored using histograms which help
you determine the capability of your process.

Histograms and Capability

Perhaps the easiest way to determine the center, spread, and shape of your
data’s distribution is with a histogram (Fig. 7-7). Histograms are simply bar
charts that show the number of times your data points fall into each of the bars
on the histogram. When you add the upper and lower specification limits, it’s
easy to see how your data fits your customer’s requirements and what improve-
ments might be necessary.

Capability Indices

Using the specification limits, there are four key indicators of process
capability.

FIgure 7-7 • Histogram of piston head diameters.