Six Sigma for Weight Loss #31

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Moving Range Chart.

I use moving range (MR) charts to assess whether process variation is in control when my data are individual measurements. The MR chart from historical weight data, "base" and "weight loss" phases, consists of:

· Plotted points for the moving range, which is the absolute value of the difference between two consecutive points.
· Center line (green), which is the average of all the moving ranges.
· Control limits (red), which are located above and below the center line and provide a visual display for the amount of variation expected in the moving ranges.

The MR chart for the weight data (Y) can be summarized as follows:

· The lower and upper control limits are 0 and 1811 g, respectively. Therefore, the moving ranges are expected to fall between 0 and 1811 g. The center line is 554 g.

· None of the individual observations fall outside the control limits. Furthermore, the points inside the limits display a random pattern. This MR chart does not provide any evidence for lack of control. Thus, the process variation is in control.

· The phases "base" and "weight loss" do not show any significant differences.

 

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